the speed boost is deactivated when you die
@Ragnarson70 I tested this by blowing myself up and it didn't remove the speed boost. But after switching sessions the boost was gone. I haven't tested getting killed by an NPC or by another player.
I'd like to offer a bit of an outside perspective here. As someone who enjoys watching speedruns rather than doing them myself, I also find this very strange and disappointing. It's like an athlete being disqualified right before the medal ceremony for violating a rule no one was aware of. I would understand if it were something that completely broke the game, but that's definitely not the case. Finding new glitches and coming up with creative optimizations is a big part of what makes speedrunning so fascinating to watch. I hope this decision is reversed.

Brazil