I agree except a forum is a different medium from Slack DMs. This is an ongoing exchange of specific, topical sorts of information. It's much closer to a Slack

I agree except a forum is a different medium from Slack DMs. This is an ongoing exchange of specific, topical sorts of information. It's much closer to a Slack channel than to DMs. DMs are a personal, often interruptive direct request for a particular person's attention and time. Some sort of interpersonal acknowledgement and appreciation of the other person's effort and time is pretty common in polite society.