I am surprised that sort of behaviour is even allowed. The places I've worked would've probably given such an employee a very strong reprimand. Then again, they've also had clear policies about not... slacking off with the company's resources.
That said, there are a few thirdparty clients; you might like the text-only ones: https://news.ycombinator.com/item?id=20500880
If Slack allowed me to ignore others, then I would be accountable for missing any important messages. I am okay with having that responsibility.
My company's approach is just that bot posts go in their own dedicated channels that anyone can mute or watch as they see fit. That works ok for us. But it doesn't give someone that option in a company that allows bot posts in any channel.
Really though, having the ability to ignore _bots_ would be quite useful, a lot of noise comes from bots that might be useful to some of my coworkers, but not others, even in the same channel.
And also ignoring highlights from particular people too
Not being able to mute or suppress doesn't necessarily need HR if everybody thinks it's quirky and harmless fun. You're then the odd man out and ostracized for trying to do your job efficiently - it's pretty bogus, but until some HN user decides to create a new messaging channel. It's gotten to the point where people will avoid seeing you in person but just as quickly ask if you "got that slack" the second they do. It's like e-mail but now you're expected to have it on your phone, home computer, work computer - never a chance to say "no" because you didn't feel like reading it at the time even as it's 9 pm on a Monday night. It's invasive and turns work banter into privatized logs of discussion - from an entry level POV this is terrible.
It's a requirement at my job, but no one is required to respond right away. Just in a reasonable time frame. Sometimes I have to wait 15 to 30 minutes before I get a response to a message and it's similar to how long people may wait for me to respond to them.
> It's gotten to the point where people will avoid seeing you in person but just as quickly ask if you "got that slack"
Before we had to start working from home, people would typically come to my desk to talk if they wanted me to look at something. If it was someone from another office, the same time frame as I described earlier for replying to a message was perfectly fine and no one complained about it. We've been using Slack for 2 years at my workplace.
> It's like e-mail but now you're expected to have it on your phone, home computer, work computer
I actually use an older smartphone that won't work with Slack (Nokia N9). It used to work when Slack had an IRC gateway, but not now. I also tell my employer that I refuse to install any work related software on my personal devices and they're fine with that. If it was that important, then they can provide me with company issued devices. So far, they haven't bothered.
As for notifications, it's up to you if you want to enable them and it applies to any type of chat client, not just Slack. I prefer just checking it periodically during work hours and any messages that I receive, I'll reply when I check for them. What you describe is a problem at the business level as opposed to a specific chat client.
For me, I would rather use a less resource intensive IM framework like IRC over Slack, mainly because it's a resource hog and frequently has significant UI lag when running it in a Firefox tab (to the point where I have to wait 3 to 5 seconds for text I type to show up on the screen).
Or you could mute notifications except for @mentions and @all and tell them to use that if they need you.