Pretty sure it's not... handicapped are accommodated differently in their class of service. I would hope that even on an upgrade this would hold true, even if some compassion is requested of other PAX... though I guess that is exceedingly in short supply these days (did I wander back into the DL forum on accident? This is a step away from want-first-book-first...). My main point is that I would try to understand the circumstance before I rejected a request out of hand... and if it's not possible to know all the details, maybe a bit of benefit of the doubt would go a long way. If it's clear that there are no special circumstances at play then, by all means, hold on to that seat (I probably would too).

I'll concede that the OP may have legit concerns/reasons that I've never personally had to consider for not wanting to be paged by name to the desk.