The internet’s best resources are almost universally volunteer run and donation based, like Wikipedia and The Internet Archive. Every time a great resource is accidentally created by a for-profit company, it is eventually destroyed, like Flickr and Google Reader. Reddit could be what Usenet was supposed to be, a hub of internet-wide discussion on every topic imaginable, if it wasn’t also a private company forced to come up with a credible plan to make hosting discussions sound in any way like a profitable venture.
Except I’ve seen a bunch of people saying they deleted their reddit history before they deleted their account, because they didn’t want reddit to be able to keep any value from their past contributions.
Now, I don’t know how many valuable comments would be impacted by that, but it is a concern for the same reasons already discussed.
I would likely do the delete post as well but I will also download my posts and comments to archive somewhere. It’s very interesting to search something and then google send a reddit link to your older post. I don’t have that much impact anyway, it’s just for my personal amusement. (like sharing my old Monster Hunter achievement or etc, nothing serious.)