I know it makes no sense, and I do understand and appreciate that you're trying to help. I'm just incredibly frustrated by this issue right now, which is ironic, given how small it is, and how successful this rather major move has otherwise been. Given that no one else on the forums is actually seeing the issue with the reactions icons, I'm going to take an educated guess and say that they've been MIA for some time, and all we/they are seeing is some rather aggressive browser caching in action. I'm guessing that new members wouldn't even notice that they're missing. Simply re-uploading the reaction icons would indeed fix the problem, but they're not included in the downloadable release of the software; I just downloaded the full version of 4.6.1, and they're not there. I suppose I could swipe them from another Invision board, which isn't such a bad idea, actually.
None of that helps with the avatars, however, but members can upload news ones I guess. Oddly, it appears at first glance to only affect a small handful so far. There's at least as many working ones that were never uploaded into the /profile subdirectory, so I'm assuming we're the victims of a mishmash of storage schemas going back over our 13+ years of using the product.
Anyway, I've logged a support ticket, just so the guys can rule out any technical issues.
Thanks again for your attempts to help, and my apologies for being grumpy.
Kev