Maybe its just that they don't understand what they are doing, I don't want to place blame on somebody for doing something unawares. But it is extremely important nowadays to keep an eye out for these kinds of things.
You know who you are. I see what you're up to.
If sidewalker is too kind too kind to speculate, I will. To my knowledge there are three reasons to actively remove an 's' from every link you post.
You have a way of tracking those links, and want to harvest metadata on users of semi-anon social media sites.
You're trying to get people used to clicking links with the "!" icon next to them, so that people will be more likely to click an actual nasty link in the future.
Your bot gets broken by https for some reason, which is why several high-post/low-comment users all stopped posting https links at the same time on multiple websites.