FWIW there's a really good Slack plugin for Weechat called wee-slack [0]. It uses the Slack API (as opposed to their IRC gateway) and so is surprisingly full featured.
Do you know whether, if I run this on an always-on remote WeeChat, it will it interfere with Slack's smart notifications (smart in that it doesn't send them when I'm sitting at my laptop with the Slack client open) either by causing them not to send when they should or to be sent when they shouldn't?
That's awesome, I'll take a look at that. Do you know if it logs to disk the same way weechat logs IRC channels? Right now I'm a little annoyed that I don't have local logs of the Slack channels I'm in.
Yes, it does - filters, logging, etc all work as they do for IRC. Huge +++ for wee-slack, has made Slack much more bearable. Supports many things Slack's own IRC protocol doesn't, like the ability to see edited messages.