I think the limit is 512 bytes, but that's including the command part that goes to the server and which doesn't show in the channel.

I agree with you though... It's especially troublesome when someone tries to make a really long argument, and winds up going "and above all, you must remember to la", without being aware that they've been cut off. If they're pasting something and it has multiple paragraphs, the end result can become almost unreadable.

Still, I wonder if this hasn't been requested before? I think it's been discussed at some point, but I can't remember when.