Can someone explain the attraction that nerds have for Slack/Hipchat over a well-tended IRC server?
IRC simply lacks important desirable features, making it poor for community building (given the existence of better alternatives). The two biggest missing features are persistence and search. Other important missing features are ease of use in terms of creation of topic-focused channels, private channels, and high quality mobile and desktop clients.
eh... slack has consistently said that large communities shouldn't use its services. - http://blog.freecodecamp.com/2015/06/so-yeah-we-tried-slack-...
Go talk to the hundreds of FOSS communities that use IRC. they have all fixed the persistence / search problem, and there is quite a few high quality mobile and desktop clients for IRC.