Hi, The chat function has been broken for a while but is now working on some versions of Limewire. I forget which versions were affected, but I seem to recall 4.12.6 was one version where the chat was totally broken.
If you see a host with a chat icon, right click and select chat with host. Possibly a chat window will pop up. which is a good start. type a message, and if things are going well you will not see a message "host unavailable". In that case send message.
With some more luck you might get a reply. The first time I did I hit block host in all the excitement. Hitting enter is a better idea
There are reasons the other host may not reply, one may be he didn't see the screen pop up. It sometimes pops up in the background. He may be away from the computer for hours on end, or just not very sociable.
The message also might fail to get through depending on how much you each are using Limewire at the time.
So the chat function is pretty flaky, but many do enable it, as it seems that it is much easier to connect with and browse host etc with a host who has chat enabled, and for that reason alone it is good to see a host with chat enabled.
So don't depend on it, but if you get chat to work, enjoy it ....
I hope that managed to explain it