To tell a little story: I've always been active in the world of big US soaps, whether on Facebook in groups or pages, or a long time ago on Yahoo! Groups. Over the decades, no one ever pointed me to a great TV series forum (this one) that I should check out; I had to find it myself eventually. So, I got into the habit of mentioning Tellytalk to someone who is actively posting about the big soaps elsewhere and seems to have a good vibe. One of these people turned out to be someone who was dearly missed here. This user checked out around the time I joined, and I noticed that back then some people were worried about that person (who was someone important behind the scenes), but apparently, that person wasn't dead or sick, that person simply had enough of Tellytalk, because that person continued posting actively elsewhere. This experience taught me that the worst fears (death, illness) aren't always correct. Sometimes people just move on and are still doing fine.
I think the fact that the top poster of the month disappears from the list for the rest of the year means that it's less noticeable when someone (big) vanishes completely. I've often thought that a particular person had been top poster of the month, only to find out later that they've been gone for months. It's a shame that January only comes once a year, because right now the top posters of the month list on the front page looks so rich, whereas in December the forum seems deserted.