My advice if you encounter people smoking on the T is to immediately contact the MBTA Transit Police at 617-600-0683. They accept text messages, and when I have had the same problem in the College Ave headhouse, they have quickly texted me back and said that an officer was on the way. I did have one circumstance where someone was smoking a joint on the platform, and when I notified the customer service agent, they went down to respond. (Though there was smoke everywhere, the agent had actually missed the culprit when walking through because they hid the joint as the official passed.) I haven't encountered loud music, but if it's obnoxiously loud I'd probably treat it the same way.
The T also has an advocate for customers, the MBTA Rider Oversight Committee. You can get their contact info at: https://mbtaroc.org/
If the ROC takes up your issue, they may be able to poke the right people at the T to improve the situation, or at least be able to tell you why the response is the way it is.
If I was still a ROC member, I would respond to a complaint like this by asking the T what the protocol is for dealing with someone smoking while loitering, whether customer service agents are supposed to patrol for this pro-actively, and find out why front-line employees seem reluctant to do anything about smoking or the pigeon infestation that is leaving poop everywhere. Are they supposed to call the Transit Police instead? I'm always on my way somewhere, so I have yet to learn what happens during police encounters. Will the police issue fines or physically remove non-compliant people? Do they offer warm shelter and treatment services to loiterers? Does the T ever get no-trespass orders taken out agains repeat offenders? It would be useful to know if people are smoking because they think no T employees are going to respond, or if they have learned from experience they aren't going to get arrested even if they commit the same offense repeatedly. I expect the Transit Police have similar problems arresting problematic people as the Somerville Police, given that the Middlesex County courts are currently dropping cases that would otherwise be prosecuted due to a shortage of public defenders. (If you think that should be fixed, you can complain to your state rep and senator about funding.)
During the summer months when there was a larger rough crowd in Davis Square, I often saw the Transit Police patrolling the headhouses at rush hour, and I actually saw them inside College Ave the other day. When they are there, I never see people loitering, much less smoking. If the the T police get a lot of complaints about misbehavior at Davis, I expect they will send officers there pro-actively more often, and the rider experience will improve.
I should say that while having to walk through a crowd of rough-looking people to get off the subway is unpleasant and puts me on guard for personal safety threats, I don't text the police about the people hanging out in the headhouses for hours if they are just resting or hanging out with their friends or poking at their smartphones, even though loitering is illegal. We have a housing shortage, and I've been stuck in a city before with no place warm to go; especially in the frigid winter weather, I have compassion for people in that circumstance. But I think if you're an illegal squatter who wants to be tolerated, it's reasonable to ask in that in return you not create unhealthy situations for other people.
I hope that we will soon get back to the immediately-pre-pandemic experience on the T, when encounters with people smoking were rare. Every time I've walked through a headhouse this week, I've encountered acrid air, either from a person recently smoking or smouldering electrical train equipment. Davis is not alone in this; I had an even worse experience at Alewife this winter, descending a stairwell full of rotting food, pee-filled clothing, bodily fluids, trash, and needles. The Globe even ran a story last week about how the station has become a dystopia and how due to lack of profitablity the MBTA just abandoned an effort to find a private-sector developer to fix up the area: https://www.bostonglobe.com/2026/01/15/newsletters/camberville-newsletter-alewife/
-B.