We talked through this and can't really see a reason for "semen" to ever appear in the HNQ list. This is in no way a statement that these questions are not generally welcome on their respective sites but, in the interest in keeping the HNQ work-safe, we feel that preventing these questions from being visible while this word is in the title is a reasonable request.
Particularly on smaller sites, the question may come and go from the HNQ list without a moderator seeing the flag. Because of this, I generally recommend editing over (or in addition to) flagging for a mod to remove from the HNQ list. If the title can be edited to remove the problematic term, that's great.
Removal from the HNQ list should be reserved for cases where the content of the question will never be appropriate for the HNQ list so if fixing the title is all that's needed, there's no reason to flag. This may be the case for most questions with "semen" in the title but I could imagine times where it'd be fine.
I do understand rene's point about having our regex get so cumbersome that it prevents benign titles from showing up but we're pretty careful about what we add to it, so I think we're unlikely to run into that problem any time soon.
Thanks for bringing this to our attention!