+--- missing tbl features -----------------------------------------------
+
+- implement basic non-parametric .de to support e.g. sox(1)
+ reported by naddy@ Sat, 16 Oct 2010 23:51:57 +0200
+ *** sox(1) still doesn't work, tbl(1) errors need investigation
+
+- allow standalone `.' to be interpreted as an end-of-layout
+ delimiter instead of being thrown away as a no-op roff line
+ reported by Yuri Pankov, Wed 18 May 2011 11:34:59 CEST
+
+--- missing misc features ----------------------------------------------
+
+- clean up escape sequence handling, creating three classes:
+ (1) fully implemented, or parsed and ignored without loss of content
+ (2) unimplemented, potentially causing loss of content
+ or serious mangling of formatting (e.g. \n) -> ERROR
+ see textproc/mgdiff(1) for nice examples
+ (3) undefined, just output the character -> perhaps WARNING
+
+- The \t escape sequence is the same as a literal tab, see for example
+ the ASCII table in hexdump(1) where
+ .Bl -column \&000_nu \&001_so \&002_st \&003_et \&004_eo
+ .It \&000\ nul\t001\ soh\t002\ stx\t003\ etx\t004\ eot\t005\ enq
+ produces
+ 000 nul 001 soh 002 stx 003 etx 004 eot 005 enq
+ and the example in oldrdist(1)
+
+- look at pages generated from reStructeredText, e.g. devel/mercurial hg(1)
+ These are a weird mixture of man(7) and custom autogenerated low-level
+ roff stuff. Figure out to what extent we can cope.
+ For details, see http://docutils.sourceforge.net/rst.html
+ noted by stsp@ Sat, 24 Apr 2010 09:17:55 +0200
+ reminded by nicm@ Mon, 3 May 2010 09:52:41 +0100