We didn't use Slack, and I think the difference was that our chat tool didn't split up the display of channels.

The thing we used had a scrolling tickertape-style window. Commit messages would scroll across once, and then they were in the history. So if you were online, you could glance at the committer, and commit message, and that was it. No need to switch to the channel, click anywhere, or do anything, it was just ... there, and then gone.

The history window was similar. It was threaded (replies indented under the message they responded to), but everything was in one list by default. So you could just skim down, and catch up on what was done pretty simply: no clicking into groups, no looking at message counts, etc.

Slack is really not the best UX, in my experience.