When I have jump boost * 255, I cant jump. But when I try to jump from a platform in a void world, I will be teleported down to void in less than 1 second. This is a bug, isn´t it???
If you want to test this bug out, open a void world with a platform, use the command /effect @p jump_boost 60 255 true, and try to jump from the platform over the void. The jump must be perfectly, so you may try a few times to be teleported down.