First of all I apologise for all this tl;dr. I promise I'm not trying to attack you; this is just an attempt to be helpful.
For what it's worth, I'm sure none of the previous anons meant to upset you with their comments. Most people in the game have been given similiar crit at one point or another, and like the first anon points out - you play a great Kamui, and people want to have CR and lengthy threads with you.
I feel I can't speak much on the issues brought up since I haven't had that many threads with you yet (which is my fault entirely), but I know I personally hesitate to poke other players about continuing threads, unless it's very plot-important, simply because I tend to assume that a dropped thread is a conscious drop on the other mun's part. If, in addition, our thread has stopped after only a few comments and without having developed into a deeper discussion I would be even more hesitant to ask for it to be continued. I think many players here might feel in a similiar way - at least I know that many in the past have expressed a reluctance to "bother" other people for threads. If I'm terribly off with this, feel free to correct me, other anons.
I'm sure no one expects you to continue every single thread for ages, or to never ever be selective in your tagging. Everyone does that from time to time, especially when castmates and OTPs are concerned, or when rl complications prevent us from focusing on rp. However, there might be other techniques, besides other people poking you to tag back, that you could try? Some people keep links to all their ongoing threads saved to make sure they don't forget any of them. Some don't delete the notifs to a thread before they've replied to it (or decided to drop it). I know you just said that you don't always have the energy to tag much at all, but implementing some of these techniques might help to give more variety to what ends up being "the closest available thread", as you put it.
I hope this was in any way helpful, and of course I hope your health will improve.