I'm not a fan of graffiti, especially not on passenger trains as it makes me unable to see the design (I love the exteriors a lot). The same goes to if companies put ads on the train's exterior. (Yes, I've seen a minimal amount of that in Berlin.) An exception might be if if the graffiti is really good, but I've never seen anything like that.
I don't know much about trainhoppers so I can't say.
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Opinion polls have officially begun!
Posting will be on and off due to school studies for a while. I am still around though and will occasionally pop in!