I noticed that in some cases in the Info makeinfo output a single space would be output at the end of a sentence. For example, after "HTML)." or "HTML.)". I'm sure that it an end of sentence shouldn't be recognized after "HTML." because you need "HTML@." for that, but I'm not sure if the cases with closing brackets are correct.
The Texinfo manual on this behaviour: "As mentioned above, Texinfo normally inserts additional space after the end of a sentence. It uses a simple heuristic for this: a sentence ends with a period, exclamation point, or question mark followed by optional closing punctuation and then whitespace, and _not_ preceded by a capital letter." (This doesn't seem to be the whole story because it doesn't cover the case of "closing punctuation" BEFORE the full stop.) We should probably follow what TeX does in such circumstances. Does anyone know?
