No. Almost certainly what happened is that the image was being regenerated after being edited, and the dagger character (the + with a long tail) used was missing from the font on the system in question. Replacing a missing glyph with a question mark is a standard thing to do, on the basis that it's something people usually notice when proofreading... but unfortunately it isn't quite so obvious when the missing character occurs at the end of a sentence.
Never ascribe to malice that which can be adequately explained by incompetence, particularly where proofreading is concerned.
Actually, I similarly believe it was likely automatically recreated by a web app; and, since it's non-obvious, no employee has questioned it--but your insight is exactly what I was hoping for. I wanted to read some interesting thought processes from YC users, exactly like that, but couldn't think of a better way to relate it to startup news at the time.
Never ascribe to malice that which can be adequately explained by incompetence, particularly where proofreading is concerned.