+- In .Bl -bullet, the groff bullet is "+\b+\bo\bo", the mandoc bullet
+ is just "o\bo".
+ see for example OpenBSD ksh(1)
+
+- .No text No ) is "text )", not "text)"
+ see the terrible example
+ case word in [[(] pattern [| pattern] ... ) list ;; ] ... esac
+ in OpenBSD ksh(1)
+
+- .Sm should *not* produce as a blank line in .Bd -literal
+ see for example "Brace expansion" in 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).
+
+- .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).
+
+- In .Bd -unfilled, .Pp should produce one blank line, not two;
+ see the ccd.conf display in OpenBSD ccdconfig(8).
+
+- .Nx 1.0a
+ should be "NetBSD 1.0A", not "NetBSD 1.0a",
+ see OpenBSD ccdconfig(8).