This has been a growing concern of mine, I've been playing poly track for over a year now and put some time into climbing the leaderboards.  Recently i was going through and watching  world records on the leaderboards for the community tracks, and i noticed that their are some people whose inputs on the display are insanely fast. Along side that their times are usually a few milliseconds faster than second place, and in a game like poly track, that's a lot . As my account name suggests i don't want to be known by real in game name, but please if anyone has extra insights on this please come out and talk about it. 
There's also the chance I'm going crazy so also let me know if I'm just horribly wrong .
Signed - someone who wants to help the community :) 

have seen (in polytrack 4.0, at least), people clip into the wall, or thin air, and disappear, and their time was 0:00.000, but that seems to be fixed. Any examples of maps that demonstrate this cheating?

SpeedySebas is in the top place in a lot of maps -- check out his old TAS channel here

So are we saying he's tasing his records? I'm a bit confused

I dunno. He seems to be near the top of almost every map, which isn't impossible for a good player with a good keyboard see histioth above,  -- I only joined PolyTrack recently, don't know much :) if you just search 'speedysebas', there are a lot of speedruns on many diffrent games, so I think he's just a really good player

I wouldn't worry too much about cheating in PolyTrack. The automated verification system catches most forms of cheating, but it's still possible to cheat with TAS or by slowing down the game.

If you have a concern about a specific run you can report it in the cheating-reports channel in the Discord server and a moderator will take a look at it!