No, seriously. I think Peeples set Mitchell's character up more carefully than that, just as he did Dehner's. It's always seemed to me that what happened to Gary exacerbated aspects of his character that the writer establishes in the first act (more or less): that he tries to control other people, including friends, in his self-interest; that he's arrogant and that his vanity is easily bruised.
The backstory about him and Kirk could have been anything, after all, that enabled Peebles to tell us what Kirk was like (let's assume that this was the more important task, for the sake of building the main character of the series)...but what it in fact was, was a deliberate story about Gary lying and using people - including his friend - and seeing nothing wrong with it. That's not an accident or coincidence, because none of this is a spontaneous recollection of real past events - it was made up to support the characterization for the story.
By the same token, while we're probably meant to accept that Mitchell actually is courageous and does consider Kirk his friend, the only reason we hear the "poison dart" story is to show that Mitchell is using it to get what he wants from Kirk now.
This is odd... are you saying that Peeples was both deliberate and frivolous in his story telling? And you get to decide which elements are the deliberate ones and which can be dismissed?
It seems by what you are saying (and I might be misreading this) is that the dart story's only
importance is to show Gary as being manipulative rather than also to further flesh out the back story of the character.
The anecdote ended by noting that he almost died
in the incident. Peeples could have used a story where Gary rescued Kirk without risking his own life... but he didn't. And I don't think it was Peeples being careless in either his writing or character development.
So am I wrong, or are you trying to have it both ways in a single post here?