Has a Fluther jelly moderator ever canceled his own question/answer because it was unhelpful, or else?

The mods can’t mod the questions in which they have a personal stake.

Maybe “deletion by co-mod”.

(1) Questions are not moderated for being unhelpful. Only answers in the General section are subject to being removed for being unhelpful.

(2) As already noted by @canidmajor, the moderators do not remove answers from questions they are actively involved in, nor do they moderate the questions themselves. We can still flag them for the others to review, of course, and sometimes we even flag our own answers if we think they might be borderline (anyone can get caught up in an off-topic tangent, after all).

(3) Moderators can send their own questions back for editing if they notice typos after the editing window has expired. This just makes the process a little less convoluted.