I am familiar with the awful TrainFX system that needlessly broadcasts PA announcements at the driver and I am in no way disputing your point which is that unnecessary distraction is poor behaviour from the guard - it is in fact part of the training, in theory, to remain to the point in order to avoid distracting the driver and I'm aware of operating incidents where announcements either auto or manual have been cited as contributory distractions.Politely -
You say it is not appropriate. That's your opinion and fair enough.
But you are not a driver. And you haven't worked these units. It is ridiculously loud, added to the welsh/English announcements the last thing you want is some pretend stars in your eyes effort.
It is pointless reporting it, as said guard is praised by the company. The easiest and safest option is to hit the switch and get back to controlling the train safely without distraction.
Drivers are taught to eliminate distraction. This is the quickest and most effective way.
Guards should be seen and not heard (at least by the person at the front) and I say this as one of the biggest cheerleaders for them.
Luckily on the new units you can kill the pa carriage by carriage. So 2/3rds of the people will suffer the waffle.
I do however stand by my point that fudging the on board equipment is not the way to deal with it and so we had best agree to disagree on the matter and move on!