Reddit has around 52 million users according to this unknown source I dug up[1]. Only the people who care the most about this situation will actually delete their posts (especially with a python script). What's that, like 500k people? So yeah only the "best" data will be removed from Reddit, but that's not even the data that makes them money. It's your data, remove it, but I think it's an illusion that it'll hurt Reddit any.
[1] https://backlinko.com/reddit-users#reddit-daily-active-users