> I have found a difference in groff's behaviour on > my home computer (groff 1.19.2) and at work (groff > 1.20.1). Note the vertical spacing and the merging > of paragraphs: [snip]
The 1.20.1 behavior is obviously wrong: in your second document, calling the header macro once breaks the behavior of subsequent calls of the paragraph macro. I'm sure this is not intended. The error must have been introduced between 1.19.2 and 1.19.3, and it's a bug in the mm macros, not in troff, as you can see by sourcing the 1.19.2 mm macros with troff 1.20.1 (and vice versa). If you edit the current mm macros and move the ....@doit call in the definition of the paragraph macro outside the conditional (as in the 1.19.2 mm macros) (and additionally delete the devtag macro calls because the seem to introduce unwanted empty lines), I think you get the correct behavior. (But this "fix" is purely trial and error, I haven't attempted to actually understand what is happening.)
