diff --git a/config/llvm.m4 b/config/llvm.m4
index c1e4bb1375..a5f4a9af44 100644
--- a/config/llvm.m4
+++ b/config/llvm.m4
@@ -91,7 +91,7 @@ AC_DEFUN([PGAC_LLVM_SUPPORT],
 
   LLVM_BINPATH=`$LLVM_CONFIG --bindir`
 
-  # LLVM_CONFIG, CLANG are already output via AC_ARG_VAR
+dnl LLVM_CONFIG, CLANG are already output via AC_ARG_VAR
   AC_SUBST(LLVM_LIBS)
   AC_SUBST(LLVM_CPPFLAGS)
   AC_SUBST(LLVM_CFLAGS)
diff --git a/config/programs.m4 b/config/programs.m4
index 21888cb68f..5a1859fd13 100644
--- a/config/programs.m4
+++ b/config/programs.m4
@@ -56,7 +56,7 @@ if test -z "$BISON"; then
 *** PostgreSQL then you do not need to worry about this, because the Bison
 *** output is pre-generated.)])
 fi
-# We don't need AC_SUBST(BISON) because PGAC_PATH_PROGS did it
+dnl We don't need AC_SUBST(BISON) because PGAC_PATH_PROGS did it
 AC_SUBST(BISONFLAGS)
 ])# PGAC_PATH_BISON
 
diff --git a/configure b/configure
index ddb3c8b1ba..5ef947ce65 100755
--- a/configure
+++ b/configure
@@ -5164,7 +5164,6 @@ fi
 
   LLVM_BINPATH=`$LLVM_CONFIG --bindir`
 
-  # LLVM_CONFIG, CLANG are already output via AC_ARG_VAR
 
 
 
@@ -9465,7 +9464,6 @@ $as_echo "$as_me: WARNING:
 *** PostgreSQL then you do not need to worry about this, because the Bison
 *** output is pre-generated.)" >&2;}
 fi
-# We don't need AC_SUBST(BISON) because PGAC_PATH_PROGS did it
 
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for flex" >&5
@@ -9979,11 +9977,7 @@ fi
 # other libraries can pull in the pthread functions as a side-effect.  We
 # want to use the -pthread or similar flags directly, and not rely on
 # the side-effects of linking with some other library.
-#
-# note: We have to use AS_IF here rather than plain if. The AC_CHECK_HEADER
-# invocation below is the first one in the script, and autoconf generates
-# additional code for that, which must not be inside the if-block. AS_IF
-# knows how to do that.
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
 $as_echo_n "checking for a sed that does not truncate output... " >&6; }
 if ${ac_cv_path_SED+:} false; then :
@@ -14926,7 +14920,6 @@ fi
 
 fi
 
-# Check for largefile support (must be after AC_SYS_LARGEFILE)
 # The cast to long int works around a bug in the HP C Compiler
 # version HP92453-01 B.11.11.23709.GP, which incorrectly rejects
 # declarations like `int a3[[(sizeof (unsigned char)) >= 0]];'.
diff --git a/configure.in b/configure.in
index 3d8888805c..96118b5e46 100644
--- a/configure.in
+++ b/configure.in
@@ -1079,11 +1079,11 @@ fi
 # other libraries can pull in the pthread functions as a side-effect.  We
 # want to use the -pthread or similar flags directly, and not rely on
 # the side-effects of linking with some other library.
-#
-# note: We have to use AS_IF here rather than plain if. The AC_CHECK_HEADER
-# invocation below is the first one in the script, and autoconf generates
-# additional code for that, which must not be inside the if-block. AS_IF
-# knows how to do that.
+
+dnl note: We have to use AS_IF here rather than plain if. The AC_CHECK_HEADER
+dnl invocation below is the first one in the script, and autoconf generates
+dnl additional code for that, which must not be inside the if-block. AS_IF
+dnl knows how to do that.
 AS_IF([test "$enable_thread_safety" = yes -a "$PORTNAME" != "win32"],
 [ # then
 AX_PTHREAD	# set thread flags
@@ -1564,7 +1564,7 @@ if test "$PORTNAME" != "win32"; then
    AH_VERBATIM([_DARWIN_USE_64_BIT_INODE],[])
 fi
 
-# Check for largefile support (must be after AC_SYS_LARGEFILE)
+dnl Check for largefile support (must be after AC_SYS_LARGEFILE)
 AC_CHECK_SIZEOF([off_t])
 
 # If we don't have largefile support, can't handle segsize >= 2GB.