So, you can only meet Abelas with vallaslin (which makes his potential comment "shadows wearing vallaslin" appropriate), and it's optional to meet Ameridan and Flemeth with or without vallaslin, depending on when you trigger the quests.
As far as I know though, only three characters will really comment if you remove the vallaslin: Josephine, Sera, and Cole. The first two will comment if you got to talk to them in Skyhold after the vallaslin is removed. They'll be surprised to see you bare-faced, ask what happened, then you can decide whether you want to tell them or not. (Sera, being Sera, isn't exactly brimming with sympathy or understanding if you tell her.) If you bring Cole with you wandering around, some party banter can potentially trigger where he tries to convinced Solas to get back together with you and comment "She is bare-faced, embarrassed" or (if you didn't remove the vallaslin), "She feels her face, marked, marred without malice."
Apart from that, I don't think anyone comments unless/until Trespasser. (I wouldn't know, I never removed my vallaslin.
)
Cassandra also has this banter:
Cassandra: I admit, I know little of their meaning, but I did not think it was possible to remove Dalish tattoos.
Solas: Most Dalish would agree with you--and see little value in doing so.
Cassandra: Then how--?
Solas: It was done in a... private moment, I would rather not discuss it.
Cassandra: Of course, I should not have asked.