I often have the situation that I asked someone something, then the next day, or next month I have the same problem again and want to search for that one link or answer without bothering everyone again. That is not possible with IRC (yet?)
They aren't deleted and gone forever. They're simply not searchable. If at some future point you decide to pay, your entire history is made available to you.
I realize that doesn't help projects who will never want or be able to pay, but it's an important point for those who might.
Turning on logging in most IRC clients is very easy. But once again this is an extra step and means learning the client a bit. One nice thing is that I can have those logs offline and search them whenever and however I like. I regularly do search my irc logs to find that links I didn't save, or re-read an important discussion.
Most things in slack are available in some form with irc, but not preconfigured out of the box. And some things on irc can take some fiddling to get set up right, and you can't count on everyone else to have enabled support.
Thing is, I use Xchat at work, on my Phone a native Sailfish OS IRC client, om my Android AndChat, on my iMac Textual and on my laptop a different instance of Xchat. And in between those clients are offline so they can't get continuous logs which they could save for offline search.
But I would love to learn how to do that, for example with ZNC which is online all the time.
That logs the logs in an SQL database, you can search with Quassel-Suche (a web-based search engine for quassel backends), and we have clients for Windows, Mac, Linux, iOS (kinda) and Android (with a better Android client in beta) and a webclient.
You get contiguous logs like in Slack, Push Notifications (with the Android beta, soon), and you can search through your logs.
In fact, I don’t bookmark things in my browser anymore – I send them in a query to myself, and just use quassel-suche half a year later to find them, or, if there hasn’t been much activity in the channel, just scroll up (infinite scroll to load more logs).
Almost everyone I work with uses ZNC. I've stuck with my same old method of tmux/screen and a text mode client. Apparently ZNC isn't hard to set up or use but I have no direct experience with it.
Mozilla solves this by having logs for the developer IRC channels by just having a bot that puts up the logs on a web server. E.g. see http://logs.glob.uno/?c=developers
Just set up an IRC log bot to log all channel traffic to a web site (can't be bothered to look one up; but I know they existed when I last messed with IRC 20 years ago).
Then you set up a bot that logs on channel (there are even dedicated services for that). Or use a client on a remote server to which you then connect (e.g. weechat).
It works mostly like this: I have a problem, let's say with QML, I log into their IRC server, ask the question and it is fixed. Then I don't work with QML for a month or two, then I remember that during the session two months ago they also linked to some cool tool but I can't find the link anymore (for example), I would like to be able to go back there and just search for my conversation. In the meantime I wasn't in that chanel or logged in into that server.
But perhaps I'm wanting too much from a chat system.