+- the "s" layout column specifier is used for placement of data
+ into columns, but ignored during column width calculations
+ synaptics(4) found by tedu@ Mon, 17 Aug 2015 21:17:42 -0400
+ loc * exist ** algo *** size * imp **
+
+- vertical centering in cells vertically spanned with ^
+ pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
+ loc * exist *** algo *** size ** imp *
+
+- support mdoc(7) and man(7) macros inside tbl(7) code;
+ probably requires the parser reorg and letting tbl(7)
+ use roff_node such that macro sets can mix;
+ informed by bapt@ that FreeBSD needs this: 3 Jan 2015 23:32:23 +0100
+ loc *** exist ** algo *** size ** imp ***
+
+- look at the POSIX manuals in the books/man-pages-posix port,
+ they use some unsupported tbl(7) features.
+ loc * exist ** algo ** size ** imp ***
+
+- look what Joerg Schilling manual pages use
+ Thu, 19 Mar 2015 18:31:48 +0100
+
+- use Unicode U+2500 to U+256C for table borders
+ in tbl(7) -Tutf-8 output
+ suggested by bentley@ Tue, 14 Oct 2014 04:10:55 -0600
+ loc * exist ** algo * size * imp **
+
+- implement horizontal and vertical alignment in HTML output
+ pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
+ loc * exist * algo * size * imp ***
+
+- implement cell spanning in HTML output
+ pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
+ loc * exist * algo ** size ** imp **
+
+- implement table borders in HTML output
+ pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
+ loc * exist * algo ** size ** imp **
+
+--- missing eqn features -----------------------------------------------
+
+- In a matrix, break the output line after each matrix line.
+ Found in the discussion at CDBUG 2015.
+ Suggested by Avi Weinstock.
+ loc * exist * algo * size * imp **
+
+- The "size" keyword is parsed, but ignored by the formatter.
+ loc * exist * algo * size * imp *
+
+- The spacing characters `~', `^', and tab are currently ignored,
+ see User's Guide (Second Edition) page 2 section 4.
+ loc * exist * algo ** size * imp **
+
+- Mark and lineup are parsed and ignored,
+ see User's Guide (Second Edition) page 5 section 15.
+ loc ** exist ** algo ** size ** imp **
+
+- GNU eqn converts some operators to special characters, for example,
+ input HYPHEN-MINUS becomes output \(mi, unless it is part of a
+ quoted word. mandoc(1) only does this when the operator is
+ surrounded by blanks, not when it is part of an unquoted word.
+ Also, check whether there are more such cases (e.g., +?).
+ reported by bentley@ 20 Jun 2017 02:04:29 -0600
+ loc * exist ** algo ** size * imp *
+
+- Primes, opprime, and '
+ bentley@ Thu, 13 Jul 2017 23:14:20 -0600