I am really conflicted on this. I agree in principal that Reddit shouldn't benefit from my years of comments and posts, but I can't count on how many times I have searched for something and found an old Reddit post or comment that was just what I needed.
Most of my Reddit comments or posts are probably not very useful, but some of it might be and I am not against other random people can find and read what I have written through the years. Reddit as a whole is a vast collection of good advice and insight that is valuable to preserve. Sure it might be archived on archive.org but that is hardly searchable for most people.