+- .Rv (and probably .Ex) print different text if an `Nm' has been named
+ or not (run a manual without `Nm blah' to see this). I'm not sure
+ that this exists in the wild, but it's still an error.
+
+- .%T should be quoted, not underlined, when .%J is also present,
+ to better distinguish the contents of .%T and .%J,
+ see for example OpenBSD cat(1)
+
+- In .Bl -bullet, the groff bullet is "+\b+\bo\bo", the mandoc bullet
+ is just "o\bo".
+ see for example OpenBSD ksh(1)
+
+- The characters "|" and "\*(Ba" should never be bold,
+ not even in the middle of a word, e.g. ".Cm b\*(Bac" in
+ "mknod [-m mode] name b|c major minor"
+ in OpenBSD ksh(1)
+
+- A bogus .Pp between two .It must not produce a double blank line,
+ see between -R and -r in OpenBSD rm(1), before "update" in mount(8),
+ or in DIAGNOSTICS in init(8).
+ Also have `It' complain if `Pp' is invoked at certain times (not
+ -compact?).
+
+- .Bd -literal and .Bd -unfilled are *not* identical.
+ In -literal, tabs are 8 spaces.
+ In -unfilled, tabs are 5 spaces, just like in -filled and -ragged.
+ See the CCDF_* display in OpenBSD ccdconfig(8).
+
+- .Nx 1.0a
+ should be "NetBSD 1.0A", not "NetBSD 1.0a",
+ see OpenBSD ccdconfig(8).
+
+- In .Bl -tag, if a tag exceeds the right margin and must be continued
+ on the next line, it must be indented by -width, not width+1;
+ see "rule block|pass" in OpenBSD ifconfig(8).
+
+- The \& zero-width character counts as output.
+ That is, when it is alone on a line between two .Pp,
+ we want three blank lines, not two as in mandoc.
+
+- When .Fn arguments exceed one output line, all but the first
+ should be indented, see e.g. rpc(3);
+ reported by jmc@ on discuss@ Fri, 29 Oct 2010 13:48:33 +0100
+
+- It seems that .TP does not want TWOSPACE after the tag;
+ see bashbug(1); reported by naddy@
+
+- Header lines of excessive length:
+ Port OpenBSD man_term.c rev. 1.25 to mdoc_term.c
+ and document it in mdoc(7) and man(7) COMPATIBILITY
+ found while talking to Chris Bennett