Thanks for clarifying -- since you're not talking about the affect it'd have on the game, and this is just your personal opinion about how the authors handled this issue, independent of whether it affects play, then it's not a play issue, it's a "What's in Crothian's head" issue. The thing he's complaining about explicitly has nothing to do with play, so I guess it's a matter of the Ebberon novels or something (where there are no PCs so this is irrelevant).
None of us have a reason to care, so there's not really any reason to refute it, either. Again, if we were talking about the affect it'd have on the game, fine, but we're not; Crothian explicitly claimed he was just giving his opinion unrelated to gaming, so he's welcome to it.
As far as how it might come up in a game -- the Eberron Campaign Guide covers it to my satisfaction. It makes it clear that a PC that has a dragonmark their race isn't "allowed" to have has essentially been touched by the Prophecy of the Dragons -- in other words, they've chosen a big ole MacGuffin as well having put a target right on their forehead. That, and the fact that NPCs are explicitly forbidden from having them, means that if the exception does come up, it's a big deal and nobody "in character" expected it to happen. That's not at all the same thing as "Take whatever, continuity be damned"; it's explictly a strange and dangerous thing for you to have a dragonmark you "couldn't possibly have" manifest.
None of us have a reason to care, so there's not really any reason to refute it, either. Again, if we were talking about the affect it'd have on the game, fine, but we're not; Crothian explicitly claimed he was just giving his opinion unrelated to gaming, so he's welcome to it.

As far as how it might come up in a game -- the Eberron Campaign Guide covers it to my satisfaction. It makes it clear that a PC that has a dragonmark their race isn't "allowed" to have has essentially been touched by the Prophecy of the Dragons -- in other words, they've chosen a big ole MacGuffin as well having put a target right on their forehead. That, and the fact that NPCs are explicitly forbidden from having them, means that if the exception does come up, it's a big deal and nobody "in character" expected it to happen. That's not at all the same thing as "Take whatever, continuity be damned"; it's explictly a strange and dangerous thing for you to have a dragonmark you "couldn't possibly have" manifest.