Like if I was doing a race on Metro in multiplayer, would it count as a valid run even if it is a multiplayer match?
If you're on about doing IL runs as long as you can show accurate timing I'm sure it shouldn't be a problem.
Generally, multiplayer matches are not allowed as runs on speedrun.com. Speedruns are meant to test individual skill and execution in completing a game as fast as possible. Multiplayer introduces too many variables that can't be controlled, such as the skill of other players or the vagaries of online play.
However, there are some exceptions. Speedrun.com allows co-op categories for some games, where multiple players work together to complete the game quickly. There are also some niche communities that speedrun multiplayer games, but these runs typically won't be accepted on speedrun.com.
