I have a modified copy (the original also) of the (dated) 1976, USD 28.tbl man(?) page written using the ms macro package. It is the only document that I have seen that describes, with a lot of examples, the format syntax for tbl(1). If it (or a modified/rewritten variant of it) could be included with groff, it would make a nice tbltut page. The modifications I made were to add a man macro wrapper so that I could put it in my manpage tree.
Would the groff folks be interested in something like this? Or is tbl passe' in the current millenia. -- aab