It’s been a bit of an ordeal because the app is *very* cross-platform, if you know what I mean, and because I insisted on running it in a VM, but Redact can delete your entire Reddit history (closing your account doesn’t). It even overwrites your comments first, which is reportedly the only way to make sure the contents do disappear.
I never did it for Twitter because I assumed (rightly) they wouldn’t actually delete anything, but somehow in this case I feel they might.
Want to know when I post new content to my blog? It's a simple as registering for free to an RSS aggregator (Feedly, NewsBlur, Inoreader, …) and adding www.ff00aa.com to your feeds (or www.garoo.net if you want to subscribe to all my topics). We don't need newsletters, and we don't need Twitter; RSS still exists.