OK so I read everything for some reason. How do you delete someone else's post?

a) You can't \b) That's not a very nice thing to say

IMO there is a place for mods which remove specific RNG if enough people are interested in running it as a separate category. For some games it could make an otherwise near-unrunnable game runnable and for others it could simply open the game up to more runners. As long as no one is kidding themselves that they can be judging such runs against unmodded runs then I see no harm.

In speed run competitions, where it is head to head, as opposed to going for records, isn't there a way to use a seed that all participants would use to be able to have random events happen the same for both of them?

Not without modding the game (in most cases) which isn't allowed in speedrunning competitively (LBs, races, GDQ-like events, etc).