I posted this on TheDonald but I think it is even more relevant here:
If you contributed to a bunch of subs on reddit, make sure you delete your posts before leaving the site. If you feel you still need contribute to subs (even if you don't want to admit it) then wait until the thread is inactive and delete your posts. I actually go one step further and edit my post with gibberish before deleting it. I have been doing this for over a year. I contributed helpful answers on tech related subs. If someone searches for an answer to something I don't want my posts coming up.
Some of you will continue to use reddit. If you must please do the above and also see my post here: https://thedonald.win/p/EMHl/dont-give-the-tech-giants-free-a/
For those of you with a long post history, there are extensions that will do the work for you. I have been deleting as I go along for over a year so I never needed one, but a quick search turned this up: https://chrome.google.com/webstore/detail/nuke-reddit-history/aclagjkmidmkcdhkhlicmgkgmpgccaod I'm sure there are more and for different browsers, so if you have one you like please post it.
EDIT: User 1776-or-1984 found this helpful tool:
Is there a nuke reddit version that will let me pick which ones to nuke? Or one that will allow me to download my post history?
https://github.com/j0be/PowerDeleteSuite