I have been present for the Q&A at several talks where I have seen the following sort of thing happen: a female member of the audience raises an objection; a male member of the audience seconds the objection in a follow-up; for the remainder of the discussion, the man is credited with the objection by the speaker and the rest of the audience (e.g. all later follow-ups refer to it as Mr. X’s objection).
It seems to me that this phenomenon can be damaging and discouraging — both the speaker and the audience are left with the impression that Mr. X scored a good point, or gave the speaker something substantial to think about or whatever, and the woman is rendered practically invisible in the discussion. This matters a lot in a profession like ours, where so much depends on being perceived as “good” and “quick” in these kinds of discussion contexts. Moreover, one can very easily be guilty of this kind of misattribution (or misperception) even if one would never tolerate any of the kinds of overt harassment or discrimination described in some of the other posts here.