Wait, I fudged, he or she has been on my ignore list in the past.
That's the thing - a few people are on my ig list permanently (unless of course they haven't posted in four years or some such and then they're erased), and a bunch are there temporarily, to give myself an anti-irritation pause. Sort of like a salve for a rash.
In those situations I'm not permanently aggravated by their existence, and their cases are apt to come up for review.
This could be a problem for me with Robert's mentioned new ignore system (not yet implemented, at least that I know of) - where the ignoree won't see you either.
My tendency to bounce on it, which works for me, would leave the ignoree thinking I left for Spain (I wish) - and then kept showing up again.