I don't think reddit let's you do this in anymore than a superficial way. I think reddit keeps the old edits internally so it won't harm the LLM. There were reports after the last protest of reddit reverting mass edits.
So basically this won't affect the LLM training but will still remove useful information and answers to questions? Wonderful...
I mean, it's the only meaningful way of punishing the company/site. It becomes unusable, people don't contribute anything further because it stops being a hub/valuable site, and eventually their costs outweigh their benefits. That last bit is probably a pipe dream, but saying "Oh well, might as well still enrich them with my knowledge/contributions" doesn't seem like an alternative.