Highly recommend purging / editing your comments before you go. I used PowerDeleteSuite for my main and alt accounts and it worked really well. If you've got thousands of comments and heaps of data it'll take ages, but it's an important step, leave them with nothing they can monetize
Yep, and just to add to this: Don't immediately delete your account afterward, keep it for a few days.
Sometimes some comments will be restored, or suddenly show up after a subreddit has opened again, or something like that (I've only had four straggler comments total, but still, wouldn't have seen that had I deleted my accounts).
I've even seen some posts about people complaining that all their content has been restored and trying to use privacy laws to get reddit to comply. Don't delete your account until you're sure everything is gone!
Besides, I would have kept my account for a little while longer anyway, because I've been lurking on reddit for the drama. ;)
Correct. It allows you to either edit or delete (or both, in which case it first edits, then deletes) all your comments, but it also allows you to filter by subreddit or date, and it even gives you the option to back up everything locally, so you don't lose everything like saved posts or something.
At the bottom, drag the big green button to your bookmark bar, then open your profile page and click the bookmark. It'll give you all the options. :) If you're not using it already, it will probably redirect you to old reddit profile page, but then you just click it again.
Edit: tl;dr deleting your account is something you'll have to do yourself, afterwards. My own account still exists, but it's been scrubbed clean of posts/comments.