+- .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.
+
+- 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), or before "is always true" in ksh(1).
+ The same happens with .Pp just before .El, see bgpd.conf(5).
+ Also have `It' complain if `Pp' is invoked at certain times (not
+ -compact?).
+
+- .Pp between two .It in .Bl -column should produce one,
+ not two blank lines, see e.g. login.conf(5).
+ reported by jmc@ Sun, 17 Apr 2011 14:04:58 +0059
+
+- If the *first* line after .It is .Pp, break the line right after
+ the tag, do not pad with space characters before breaking.
+ See the description of the a, c, and i commands in sed(1).
+
+- If the first line after .It is .D1, do not assert a blank line
+ in between, see for example tmux(1).
+ reported by nicm@ 13 Jan 2011 00:18:57 +0000
+
+- .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).
+
+- When the -width string contains macros, the macros must be rendered
+ before measuring the width, for example
+ .Bl -tag -width ".Dv message"
+ in magic(5), located in src/usr.bin/file, is the same
+ as -width 7n, not -width 11n.
+
+- 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.