Is there any way to claim old usernames?
I saw an account which hadn't been online for 4 years and had no forum posts/runs.

If you're talking about Aris idk, says they have 2 runs, though have they been pending for 4 years, or did the leaderboard disappear? I imagine the problem with purging old usernames is the risk of hurting leaderboards. People tend to pick up speedrunning as a hobby and then quit all the time. I get this person has no runs visible, an exception could probably be made though.

Yeah, the profile info page says that it has 2 runs but the main page doesn't show anything.