At least part of the ethics problem here is that it'd be plausible to conduct this research without creating any new posts. There's a huge volume of generative AI content on Reddit already - and a meaningfully large %ge of it follows predictable patterns. Wildly divergent writing styles between posts, posting 24/7, posting multiple long-form comments in short time periods, usernames following a specific pattern, and dozens of other heuristics.

It's not difficult to find this content on the site. Creating more of it seems like a redundant step in the research. It added little to the research, while creating very obvious ethical issues.