Are sexual innuendos an absolute no-no in either questions or answers or comments, even if they are humorous?
Let's face it, there's a lot of it about. By any reasonable definition, that's a sexual innuendo (you can decide for yourself whether it's "humorous", but I hope no-one's actually "offended").
I haven't noticed many gratuitous innuendos in questions or answers since I've been on ELU. But even though my personal standards are pretty low in this area, I'd tend to edit them out if I thought they might be considered offensive by some visitors.
I'm not a mod, so I don't really know how often it's used, but I would just point out that when it comes to flagging for moderator attention, the first of five possible choices is...
I am flagging this comment as rude or offensive
Given that "offence" is a subjective thing, I would expect the mods to be extremely sympathetic to any user's complaints in this area. That's to say I think they should err on the side of caution, and delete/edit any text which someone finds objectionable, even if they themselves don't find the material particularly offensive.
The bottom line, as Reg comments, is that superfluous text shouldn't be posted, and may be removed. It's therefore a judgement call for the mods, and thus far I've no complaints.