Saw the same thing happen recently to a project made by friend of mine (and no, it was genuinely a cool project, and it isn't me trying to tell a personal story under a guise of it being done by a friend; I would love to take any amount of credit for it, but I had zero involvement whatsoever).

The project was basically a wordle-like game, but for chess puzzles. It was focused less on being an actual chess puzzle game (i.e., tricky chess game positions that lead to a decisive turnaround) and more on actually training to improve your blunder game (i.e., each puzzle was more of a "pick a move that isn't a blunder given a scenario from a real lichess game").

He made a post on r/chess, it gathered a small number upvotes, there were a few comments left along the lines of "omg this is so awesome, this is helping my anti-blunder skills a lot, had no idea I wanted this until I saw it." And no, I didn't leave a comment, but I upvoted the post. It didn't feel right to brigade a post with my positive comments on it as a friend, especially given how anal reddit mods can get about this in some cases.

Next thing I see, mods just removed his post with a "no promotion allowed" reasoning. The website had no ads, no paid components, not even a name/profile of my friend attached to it (so no self-promotion angle either; he is gainfully employed and isn't looking for a job). He did it purely for the love of the game, some subreddit users clearly found it helpful, and yet the mods just deleted it.