The Groff info manual Section 5.1.3 Sentences says groff only recognizes end of sentence characters at the end of line. Other places in the manual mention that recognition of end of sentence characters also happens when the followed by two spaces.
Section 5.1.3 should be changed to mention that end of sentence characters are also recognized when followed by two spaces. Especially since the Concept Index links to that section for many of the discussions about sentences, sentence spacing, and characters and symbols treated transparently while handling end of sentence characters. (Is it better to start discussions of things like this on the mailing list or as a bug report on savannah.gnu.org?) -- T. Kurt Bond, tkurtb...@gmail.com, https://tkurtbond.github.io