Forwarding this here since the forums in question are effectively dead as a graveyard, explained below: forum.speeddemosarchive.com/post/account_delete_request.html

As explained, I have been unable to personally delete my own SDA forums account, forum.speeddemosarchive.com/post/how_do_i_delete_my_account.html the popular theory being it's vulnerability to abuse, interpret that however you want, story and debate for another date and time. I have an account on those forums that needs to go, not explaining why. Furthermore, I have an account on Speedrunslive that also needs to go. While I intend to maintain the account I have here at Speedrun.com, the aforementioned sites outside of this one have accounts that, again, need to be disposed of, once and for all.

No funny tricks, no backup accounts, no second thoughts, no questions asked, simply gone and forgotten. Point and judge all you want, I would personally prefer no one ask why, specifically due to how irrelevant it is. If anyone knows or happens to be an active moderator or administrator of either of those sites, I request the deletion of the accounts on both of those sites, that is, all but Speedrun.com. If you need information pertaining to the usernames on either of those sites, I will provide it at that time, but not before receiving a response confirming I am, in fact, in direct contact with either a close associate of any active moderators or administrators or they themselves.

All of this, just to say: If not for the slightly understandable imminent problems that would stem from allowing people to delete their own accounts, I would have done so without anyone ever noticing.

Summary: Requesting deletion of accounts on SDA forums and Speedrunslive, unable to perform action manually, would have tried without anyone knowing if not. This is not a request for account deletion from Speedrun.com, please do not interpret it as such in any way, shape or form.
SDA forums: forum.speeddemosarchive.com
Speedrunslive: www.speedrunslive.com

If you want to delete you account in those sites, go and request it there somehow.
speedrun.com ownership is not related to those sites, no one here can help you.

I mean, lots of people who have used SRL have used speedrun.com, so it's not really that bad of a place to just ask questions about it. Reaching out to the people who run SRL would be best, though. And as oreo said, staff for this site obviously cannot just go and delete accounts on SDA or SRL because they are not the same people. Since the sites are pretty dead, it's hard to say whether or not you'll be able to delete any of that stuff.