I must say BestWestern is getting it closest to my opinions on the subject. It's important for customer-facing crew, be they conductors/guards/TMs/revenue staff to patrol trains at any time of day, and it's important that issues such as vomit on doors don't get worse. I hate to be a "grass" but sometimes you have to hope that passengers take the time to comment on whether or not certain colleagues are providing the necessary presence. Some TOCs, some depots and certainly some individuals are better than others. Best practice is what needs to be identified.
Vomit and other bodily fluids are tricky things to assess. Whether it's fire escape routes, problems with them getting in door mechanisms, seating capacity, or an inability to get to individual door locking equipment necessitating a full-blown cancellation, or many more factors, each situation varies hugely and likewise the actions involved. I do agree that somebody at any given TOC involved needs to take charge, and somebody patrolling the train is best.
What I would add is that some trains are very hard to patrol due to the absence of equipment such as door controls, or station dispatch positions. It's always the way that the train which needs most patrolling, or is least able to cope with drunk people on a weekend night, is also the one which requires the guard/conductor to head to their back cab every few minutes because nobody's bothered to fit saloon controls.
In my time so far on the railway, there've been plenty of trains I'd have liked to see patrolled better and many of my colleagues think likewise. Sometimes the technology isn't there yet. There are other remedies - some stock does let conductors view CCTV in real-time, for example - but very few of them are universally available across the network.
Lastly, when patrols of trains can happen, uniform doesn't have to be a red rag. Yes, you are the most visible person, and yes, someone will invent a song based on your name badge. But with decent customer interaction skills, almost anything can be turned around to gaining co-operation. You're railway staff and issued with a big bunch of keys, on the top of which I put a big bottle opener (not for my own use, of course...). You see a PA system, I see that if the train's delayed I can get people to go for a walk and come and have a chat by telling them where I am. Big orange bag? Pop a cheap phone charger in there and you'll even get faredodgers co-operating when they need to text whoever it is from Random Suburb of Kent. You get the picture. Then when you need to get co-operation, it's all there waiting. There'll be a lot of noise and "oh, mate, REALLY?", but it'll happen.
I don't expect conductors/guards or anyone else to put up with anything which causes them a health hazard, nor serious attempts at crime. I've cancelled trains because conditions were unsanitary and I've never tried to clean up vast pools of vomit (etc.) without the right equipment. It's asking for trouble and it'll only make people more likely to get residue of it smeared on them by mistake, anyway. However, I will always try to work around it and always try to create conditions where people instinctively don't mind being a friend rather than an enemy. Some folks will always try to defraud or vandalise the railway and I have no time for that, at all, ever, but if it's been a heavy night out then you need to be there to cope with it, and there to help passengers cope.
Regarding the complaint, I'd love these things to be easier to sort out. Next time, try flagging down the guard when they step onto the platform, use the BTP text number if you can't, and if the train has stickers with a "Customers can report such-and-such faults" scheme, use that too (where I'm based, that goes straight to the roving fitters). If the doors are obstructed you may wish to use the alarm, but try to speak to staff first in any way possible. Never try to calm down disorderly people without the right training either. It's not worth the risks.
