diff --git a/src/backend/access/brin/brin_inclusion.c b/src/backend/access/brin/brin_inclusion.c
index 332a854af6a..86788024ef6 100644
--- a/src/backend/access/brin/brin_inclusion.c
+++ b/src/backend/access/brin/brin_inclusion.c
@@ -432,7 +432,7 @@ brin_inclusion_consistent(PG_FUNCTION_ARGS)
 			 * It is straightforward to support the equality strategies with
 			 * the contains operator.  Generally, inequality strategies do not
 			 * make much sense for the types which will be used with the
-			 * inclusion BRIN family of opclasses, but is possible to
+			 * inclusion BRIN family of opclasses, but it is possible to
 			 * implement them with logical negation of the left-of and
 			 * right-of operators.
 			 *
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 4004468fa01..fad859a812e 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -2208,7 +2208,7 @@ SetMultiXactIdLimit(MultiXactId oldest_datminmxid, Oid oldest_datoid,
 	 * space, but that's not really true, because multixacts wrap differently
 	 * from transaction IDs.  Note that, separately from any concern about
 	 * multixact IDs wrapping, we must ensure that multixact members do not
-	 * wrap.  Limits for that are set in DetermineSafeOldestOffset, not here.
+	 * wrap.  Limits for that are set in SetOffsetVacuumLimit, not here.
 	 */
 	multiWrapLimit = oldest_datminmxid + (MaxMultiXactId >> 1);
 	if (multiWrapLimit < FirstMultiXactId)
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c
index 4a86fbc1c1e..968506dd516 100644
--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -390,9 +390,9 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
 
 	/*
 	 * Try to attach to the segment and see if it matches our data directory.
-	 * This avoids shmid-conflict problems on machines that are running
-	 * several postmasters under the same userid and port number.  (That would
-	 * not ordinarily happen in production, but it can happen during parallel
+	 * This avoids key-conflict problems on machines that are running several
+	 * postmasters under the same userid and port number.  (That would not
+	 * ordinarily happen in production, but it can happen during parallel
 	 * testing.  Since our test setups don't open any TCP ports on Unix, such
 	 * cases don't conflict otherwise.)
 	 */
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index dd16938d9c7..688ad439edb 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -4743,8 +4743,8 @@ retry:
 	}
 
 	/*
-	 * Queue a waiter for to signal when this child dies. The wait will be
-	 * handled automatically by an operating system thread pool.
+	 * Queue a waiter to signal when this child dies. The wait will be handled
+	 * automatically by an operating system thread pool.
 	 *
 	 * Note: use malloc instead of palloc, since it needs to be thread-safe.
 	 * Struct will be free():d from the callback function that runs on a
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 69beaf2ab50..13d5cb083c3 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -211,7 +211,6 @@ Generic_Text_IC_like(text *str, text *pat, Oid collation)
 
 	if (pg_database_encoding_max_length() > 1 || (locale && locale->provider == COLLPROVIDER_ICU))
 	{
-		/* lower's result is never packed, so OK to use old macros here */
 		pat = DatumGetTextPP(DirectFunctionCall1Coll(lower, collation,
 													 PointerGetDatum(pat)));
 		p = VARDATA_ANY(pat);
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 9f0bede93b9..63f554307cd 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1681,12 +1681,7 @@ GenerateRecoveryConf(PGconn *conn)
 	initPQExpBuffer(&conninfo_buf);
 	for (option = connOptions; option && option->keyword; option++)
 	{
-		/*
-		 * Do not emit this setting if: - the setting is "replication",
-		 * "dbname" or "fallback_application_name", since these would be
-		 * overridden by the libpqwalreceiver module anyway. - not set or
-		 * empty.
-		 */
+		/* Omit empty settings and those libpqwalreceiver overrides. */
 		if (strcmp(option->keyword, "replication") == 0 ||
 			strcmp(option->keyword, "dbname") == 0 ||
 			strcmp(option->keyword, "fallback_application_name") == 0 ||
diff --git a/src/bin/pg_rewind/t/RewindTest.pm b/src/bin/pg_rewind/t/RewindTest.pm
index 61904f25ff4..68b6004e946 100644
--- a/src/bin/pg_rewind/t/RewindTest.pm
+++ b/src/bin/pg_rewind/t/RewindTest.pm
@@ -26,11 +26,7 @@ package RewindTest;
 # still running.
 #
 # The test script can use the helper functions master_psql and standby_psql
-# to run psql against the master and standby servers, respectively. The
-# test script can also use the $connstr_master and $connstr_standby global
-# variables, which contain libpq connection strings for connecting to the
-# master and standby servers. The data directories are also available
-# in paths $test_master_datadir and $test_standby_datadir
+# to run psql against the master and standby servers, respectively.
 
 use strict;
 use warnings;
diff --git a/src/bin/pg_upgrade/TESTING b/src/bin/pg_upgrade/TESTING
index 6831f679f66..e69874b42d0 100644
--- a/src/bin/pg_upgrade/TESTING
+++ b/src/bin/pg_upgrade/TESTING
@@ -36,7 +36,7 @@ Here are the steps needed to create a regression database dump file:
 
 1)  Create and populate the regression database in the old cluster.
     This database can be created by running 'make installcheck' from
-    src/test/regression.
+    src/test/regress.
 
 2)  Use pg_dump to dump out the regression database.  Use the new
     cluster's pg_dump on the old database to minimize whitespace
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 6788f882a84..38236415bef 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -105,7 +105,7 @@ get_control_data(ClusterInfo *cluster, bool live_check)
 #ifndef WIN32
 	pg_putenv("LANG", NULL);
 #else
-	/* On Windows the default locale cannot be English, so force it */
+	/* On Windows the default locale may not be English, so force it */
 	pg_putenv("LANG", "en");
 #endif
 	pg_putenv("LANGUAGE", NULL);
diff --git a/src/fe_utils/string_utils.c b/src/fe_utils/string_utils.c
index 58610dbf572..d5757becef2 100644
--- a/src/fe_utils/string_utils.c
+++ b/src/fe_utils/string_utils.c
@@ -541,8 +541,7 @@ appendShellStringNoError(PQExpBuffer buf, const char *str)
 
 /*
  * Append the given string to the buffer, with suitable quoting for passing
- * the string as a value, in a keyword/pair value in a libpq connection
- * string
+ * the string as a value in a keyword/value pair in a libpq connection string.
  */
 void
 appendConnStrVal(PQExpBuffer buf, const char *str)
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 75088f83632..a9a92de2470 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -383,7 +383,7 @@ tas(volatile slock_t *lock)
 	register slock_t _res;
 
 	/*
-	 *	See comment in /pg/backend/port/tas/solaris_sparc.s for why this
+	 *	See comment in src/backend/port/tas/sunstudio_sparc.s for why this
 	 *	uses "ldstub", and that file uses "cas".  gcc currently generates
 	 *	sparcv7-targeted binaries, so "cas" use isn't possible.
 	 */
@@ -598,7 +598,6 @@ tas(volatile slock_t *lock)
 
 
 #if defined(__mips__) && !defined(__sgi)	/* non-SGI MIPS */
-/* Note: on SGI we use the OS' mutex ABI, see below */
 /* Note: R10000 processors require a separate SYNC */
 #define HAS_TEST_AND_SET
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 1a14a4a0a7e..c8b8d070395 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -736,7 +736,7 @@ static void
 destroy_ssl_system(void)
 {
 #if defined(ENABLE_THREAD_SAFETY) && defined(HAVE_CRYPTO_LOCK)
-	/* Mutex is created in initialize_ssl_system() */
+	/* Mutex is created in pgtls_init() */
 	if (pthread_mutex_lock(&ssl_config_mutex))
 		return;
 
diff --git a/src/test/recovery/t/013_crash_restart.pl b/src/test/recovery/t/013_crash_restart.pl
index ac6d9653af9..3ecb9dd4df7 100644
--- a/src/test/recovery/t/013_crash_restart.pl
+++ b/src/test/recovery/t/013_crash_restart.pl
@@ -90,9 +90,9 @@ $killme_stdout = '';
 $killme_stderr = '';
 
 
-# Start longrunning query in second session, it's failure will signal
-# that crash-restart has occurred.  The initial wait for the trivial
-# select is to be sure that psql successfully connected to backend.
+# Start longrunning query in second session; its failure will signal that
+# crash-restart has occurred.  The initial wait for the trivial select is to
+# be sure that psql successfully connected to backend.
 $monitor_stdin .= q[
 SELECT $$psql-connected$$;
 SELECT pg_sleep(3600);
@@ -171,10 +171,9 @@ ok(pump_until($killme, \$killme_stdout, qr/in-progress-before-sigkill/m),
 $killme_stdout = '';
 $killme_stderr = '';
 
-# Re-start longrunning query in second session, it's failure will
-# signal that crash-restart has occurred.  The initial wait for the
-# trivial select is to be sure that psql successfully connected to
-# backend.
+# Re-start longrunning query in second session; its failure will signal that
+# crash-restart has occurred.  The initial wait for the trivial select is to
+# be sure that psql successfully connected to backend.
 $monitor_stdin .= q[
 SELECT $$psql-connected$$;
 SELECT pg_sleep(3600);