Hmm... your post is useful for others who are considering Mattermost -- certainly may help others who have similar priorities. That said, I think you could have made the same point without being negative about other product. You aren't trying to be negative, but it does come off that way. I think you could make the same statement and impact without even mentioning Slack or its negatives in your case -- just focus on the positives of Mattermost for your use case.