A rude reply in my hiking forum has me questioning moderation styles

Someone posted a trail tip and got a snarky 'everyone knows that' response, which made them delete their account. I help run the forum and missed it until after the damage was done. I'm torn between letting people speak freely and stepping in more often. What's your take on keeping things friendly without too much control?

I tried composting inside, now my apartment hosts a fruit fly family reunion.