Using texinfo.tex 1999-09-25.10, Debian texinfo 4.0 and a recent tetex, I noticed that the document below when put through texi2dvi gets a line break in between the "_" and "foo" of "_foo_bar". That seems undesirable to me since a lone "_" on a previous line could be easily missed when skimming through a document. This seems to occur only rarely. It only happened for me inside an @table, but I've got no idea whether @table has anything at all to do with it.
foo.texi