Hello! I do operate a Slack and Gainsight community. RSS feeds post content into channels in Slack from GS community. Members utilize Slack as their instant messenger to communicate amongst themselves. It does make it harder having to cross post some communications however with RSS feeds that might be able to help.

There are a few community platforms out there that offer a way to cross moderate posts on a single platform. I think this is a little overkill if you can keep an eye on things but do understand the need for it on large scale organizations. 

Users like it because most already have slack installed on their CPU and can have it open throughout the day where it auto updates vs hitting refresh on a webpage.