Good observations.
I'll fix the debug info and the server string.
Note, though, that the debug info should only be printed in debug builds, not in release.
i found a funny bug (for 1.3.1/1.3.2 users) but its hard to explain so i made a video

(the bug is not that i am using the same username but that i have different skins

)
I've seen that bug before where the name of the player suddenly appeared somewhere else, and the sky turned all haywire for me. I'm not sure what fixed it or where the bug was :/
its becouse the 1.3.1 client holds a block in his hand but the 1.2.5 client doesn't know that block. you can try it yourself

i used a diffrent launcher that allows me to use diffrent minecraft.jar's at the same time. its called magic launcher. thats how i created this video

It amazes me every time how Minecraft has almost no error handling whatsoever.. the fuck man O_o
How the heck can an unknown block cause the player name to appear upside down somewhere else
Can someone confirm that there is no sound of the block being placed in 1.3.2 and mcserver?
i can confirm it. it doesn't work anymore

Well I ain't fixing that

I think having the possibility of two players with different versions is weird enough; fixing all minecraft's problems? no way.
Btw. rev 841 should have both styles of authentication working.
can you than fix that when a 1.3.2 client places a 1.3.2 block (like a block of emerald) the 1.2.5 client crashes?

maybe can you do that when someone places a 1.3.2 block the 1.2.5 client sees a stone block or something.
Definitely not. Even if I fixed the placement, the next time the client connected, they would get that block anyway, unless MCServer checked every single block before sending a chunk. Not gonna happen.