I wouldn't suggest GWR▸ stop using Twitter as it's a good way for their passengers to get info at times of disruption. But drop Facebook as every time they run a Famous Five promotion it just fills up with negative comments about the service.
However if they wanted to could turn off commenting to prevent trolling
You need to learn the difference between "trolling" which is frequently a subjective judgement & customers expressing legitimate dissatisfaction with poor service and dismissing the latter as the former.
The twee, condescending nature of the "Famous Five" campaign which has now launched 1000 parodies is one of the factors which provokes angry responses, especially at a time when the service is so woeful.
Sorry but most of this woeful services is around London & Bristol, i.e the busiest bits of the network. Devon has a fairly decent services, with occasional 2 or 3 minute delays (some people seem to go mad in Reading if its that late). The other week, I went from Devon to Reading, down to Oxford, back home again via Reading, and the only delay I had was the train from Reading back to Devon. To me thats good considering how many trains run during the day.