If someone is reducing the S/N of a large channel then it is a culture problem that needs to be solved by the management. I have seen a few Slack dramas like that in companies I worked with (e.g. a person trolling), and it wasn't difficult to solve. Letting team members to arbitrarily block each other seems insane to me from a company standpoint.
There are 850,000 people on my work Slack. I do not need to talk to all of them, much less read what all of them have to say.
> What's next, jumping off the daily standup call for a while when a colleague you have a problem with is speaking?
No that's not next, and I think the goalposts you're looking for are way back over here.
I don't disagree that Slack can be a vector for "culture" problems. I don't see why it follows that employees should be deprived very simple tools that allow them to fix the symptoms themselves if their employer disagrees or doesn't care.