I think Microsoft bundling IE is a very valid comparison.

I guess it's hard to see what's a transparent attempt to crush Slack and what's just the regular enhancement of business. After all, you can hardly buy Word alone and no one complains.

The problem I run into here is that somehow relying on antitrust prosecutorial discretion does kind of make it hard to innovate, since you might be unsure about the line between outcompeting and being anticompetitive. Slack drove HipChat out of business because it was frankly terrible. But I do think the lawyers can mostly figure this out.