Recently, I have met several players, who do this at games:

Me: 3hk
Him: liar
Him: I hit you

So, I decided to write this small post that explains what 3hk's mean.

3hk = A player who sees his own health as 3 gets killed.

The situation goes like this (sorry, going a bit technical):
Player B sends an ammo packet to the server, and the server sees that he hit Player A.
The server sends the hit packet to all players.
Player A doesn't receive the packet due to packet loss (network lag).
Player A doesn't know that he got hit, and thus he sees his health 3.
Player B sends more ammo packets.
Server sees that Player A got hit again.
The server sees that Player A's health is now 0, so it sends the kill packet to Player A.
Player A sees that he goes straight from 3 health to 0 health, and dies.

Player A: 3hk
Player B: no, i hit u

I hope this clarifies some stuff.

you're smart

I thought this was going to be about why people feel so compelled to report them, especially in games with more than two players.

You've still got no way of proving that they are or aren't lying though, so I really do not think this is an issue in the slightest. Fair enough if you're going to give the other player benefit of the doubt and be courteous, but in tournament games it just seems like an easy way to cheat.

That's why most tournaments tend to add a rule that says 3hks count

There is in fact a way to prove it, at least in some cases. If a player gets hit and blinks, but does not display the hurt animation and doesn't seem to be affected in movement by the bullets, then you can usually assume they have fake health and will get a 3hk.

Anyway, a solution for the problem of fake health and 3hks would be for BlurredD to add a new kind of packet, the health packet, which would be broadcasted every few seconds (in addition to the usual hurt/heal packets) and would update the local health bar of all players. Fake health would only occur until the player successfully receives the health packet.

Originally Posted by GLaDOS

A solution for the problem would be for BlurredD to...

By the time blur starts working on plus again, the jj2 source code will get released already...

Originally Posted by GLaDOS

There is in fact a way to prove it, at least in some cases. If a player gets hit and blinks, but does not display the hurt animation and doesn't seem to be affected in movement by the bullets, then you can usually assume they have fake health and will get a 3hk.

That may be so, but it still doesn't stop players attempting to lie about being 3hked.