So, in the process of deciding to work on purging more of my content from parts of the internet that I just no longer agree with, time for Reddit to go. I create it back when I started my blog, have met some interesting people there (many of who post here on occasion), and… the place is unrecognizable lately.
The new interface appears to have utterly ruined the place, focusing more on video content than the text that made it sane, and the mods have gotten rather insane, I’m banned or shadowbanned from a few places for daring to post links to stuff I’ve written externally instead of writing the same post over and over and over and over again, and there’s been a mass exodus of technical posters over the past few years, as far as I can tell (in that the people giving advice in solar/battery subreddits don’t know their head from the wrong end of a lithium runaway, etc).
Thus, notes on the removal process.
Reddit Power Delete Suite
Installs via a bookmark and works magic with Javascript.
The export feature on this simply doesn’t work with a long posting history. It pulled 76k of content, via a data:text/csv; hyperlink, which is utterly incomplete.
Nuclear Reddit
Harder to set up, requires Python3, ffmpeg and a few pip packages. Also, your username/password, and API access. It chews for a good long while saving out posts in a sane format (text) you can review later.
On the other hand, it doesn’t save comments on sufficiently old posts for some reason. Before about mid-2017, submissions just don’t have comments archived out. Not that I really care…
We’ll not discuss just how much time I’ve apparently spent on Reddit, but… definitely a lot based on my submission and comment count. 164 submissions, 11993 comments. 
Though only 77k words in comments, apparently…
I’ve decided on a two pass approach, based on editing comments first, then deleting things. So, after it’s saved everything and you’ve verified it, run the delete option with “Edit comments, leave submissions.” This will overwrite your comments to some fixed string, which may help prevent finding the deleted data at places like https://removeddit.com/ - though I wouldn’t fully rely on that. Reddit claims to only store the latest version of the comments, though, of course, there are the various backup sites on the interblags. Shouldn’t have posted anything sensitive, though, right?
Then, run again with “Delete comments, delete submissions.” Not that it has gained much, but… feels cleaner.
The comment editor seems to be broken for me, so just modify the script and replace the strings with something or other. You almost certainly will not want to link Ruqqus as in the default script, as the place seems… sketchy would be a polite term.
Also, there are a few bugs in the comment overwrite code. It’s Python, fix it. I’ve filed a bug.
Mmm… progress.
This will take a long while.
Once that finished, I ran it again, deleting the edited comments and submissions. Experimentally, there were a few comments it missed for some reason - but it did cover most of them.
Save your backups off, if you care about them, because they’ll get overwritten if you run it again.
Run it again, delete everything. The magic incationtation is DELETE USERNAME - replace username with your username, no square brackets, all caps.
Let it run, it’ll take a while longer.
This… also didn’t delete everything. It claimed to remove submissions, but didn’t seem to actually get all of them, and also missed some comments.
However, it cleaned out enough that PowerDelete was able to work some magic for a while. And get almost all the submissions removed.
It couldn’t clear everything, but it left little enough I was able to clear the rest out by hand.
Result?
The drama has been fun to watch from a distance.