Help: chat-keep-count
Tcl 2014 Conference, Portland/OR, US, Nov 10-14
Send your abstracts to tclconference@googlegroups.com by Sep 8.

The "chat-keep-count" setting:

When /chat is cleaning up older messages, it will always keep the most recent chat-keep-count messages, even if some of those messages are older than the discard threshold. If this value is zero, then /chat is free to delete all historic messages once they are old enough.