I would argue that Momo's chassis has a sex. Pintsize's doesn't. But if Momo was switched to a male chassis and didn't have the gender switch flipped in the software, would you (plural you, open to anyone) call Momo he or she?
I'd say that a male-chassis Momo, while the gender switch was set to female (BTW, ChaosWolf, for the sake of the experiment, let's say that Momo chose the male chassis, and also chose to keep the gender switch set to female, so as to not weasel out of classifying this) would be something along the lines of a female cross-dressing as male (given the ease (even if it's expensive) of switching chassis, it's almost as easy as a human changing clothes) in human terms?
And, something I edited into my previous post, then saw replies, so I removed it:
Another thing I realized, but this goes into an earlier discussion on these forums about the timeline of robots getting equal rights versus the timeline of the story... if you combine the more recent assertion that AIs become partners with their humans (not in that way!) via a contract, and that robots have equal rights, with Marten's statement in #347, things start to get odd - the robot's partner can set a gender for the robot upon entering the contract at the very least? That would indicate a
gender change, as the AI isn't created for the human specifically on first boot of the AnthroPC, the AI is paired with the human and installed in the chassis. (And, it's implied that it's a setting (similar to Pintsize's language settings that changed personality significantly), meaning it could be changed at will by the owner (and I do mean owner in this instance), at least on pre-AI rights software.)
(IIRC, the way that the forums resolved the dichotomy between Jeph's handling of the human/robot relationship before and after Momo was either, AIs got equal rights not long before Momo was introduced (making it a VERY recent event in the QC verse, likely less than a year (QC time) ago), or that many AIs, Pintsize and probably Winslow included, didn't actually care about equal rights (IIRC that was actually discussed in-comic, too, that Pintsize and Winslow didn't want the responsibility).)