Content on a personal blog should not be edited

I mostly agree with this, with a few caveats. My personal blogs/newsletters over the years have sometimes really just been rambling journal entries. That content, I just look over for web typography, grammar, spelling and things like correct HTML entities for accents. I will always fix typos as I notice them but in general I don't put a lot of effort into tightening or improving the content.

But in the same "stream" of content there are often reviews, long essays, or discussions on programming, often including snippets of source code. In those pieces I often will go back and tighten up my arguments, edit for clarity, and update code for bugs or style issues that bug me later. I've done this especially as I migrate my material from Blogger blogs to my own server and turn it all into Markdown source that I maintain and build with my own Makefiles. Once it's in this personal system, it also goes into Git, so if I want to compare versions over time I can at least do so that way, going back to the point it was migrated. Or I can look at Internet Achive's snapshots.