When someone makes a vent post, regardless of how triggering it may be, do not just lock it and link a hotline. That is very dangerous for the person venting, because it could make them think that their problems shouldn't be talked about and they will internalize that. Instead, moderate the vent and make sure that everyone is responding in a respectful manner, and that nobody is getting too triggered. If someone is getting triggered, give them a polite recommendation to get off the vent post and calm themself down. Also make sure said vent (and the replies) have proper trigger and/or content warnings.
Tl;dr- Don't just lock and link hotlines to vents, because it can make the situation much, much worse.
Edit: Grammar.