As of recently, your Reddit comments can disappear completely if a user blocks you fast enough, even if they are still posted.

I noticed this a few days ago. Some dumb troll blocked me right after I posted a comment, but I noticed something very unusual: my comment disappeared completely in my feed. As you cannot see posts or comments of blocked users on the account you've been blocked on, the only way I could access it is if I went back on the page on a different browser. And there it was.

This has never happened before, and with Reddit having changed how the block function appears since some months ago (like late 2024 or so), I believe this is a new change. And possibly a fatal flaw, since Reddit is the type of site that lets you see everything you've ever posted (as long it doesn't exceed longer than a decade)

So be warned, you can now lose complete track of your comments even if you just posted them.