the stars like dust

10 elements of Kavanagh’s characterization that fanon frequently gets wrong. At least possibly.

(By “wrong” I mean in disagreement with my own reading of canon.)

1. The man's not stupid. He is very intelligent. It is quite possible that, without his insight, the team might not have survived “38 Minutes”.
2. Kavanagh's not useless to Atlantis. His contributions to the mission have been valuable. See above.
3. The ponytail is not ugly to everyone; there are many folks, myself included, who find long hair on a man beautiful. Which brings me to:
4. He isn't ugly to everyone in general. Although the clothes he wears and the tight arrangement of his hair is unflattering, a discerning eye can easily see he would look fantastic with a little sartorial attention.
5. He isn't always wrong. His assessment of Weir’s leadership is well-founded; she handled him extremely poorly for a supposedly brilliant diplomat. Even if one agreed with her opinion of him as a coward, there is no logical reason to waste him as a resource by openly insulting and alienating him. Cowardice is not in and of itself a quality that makes a scientist’s skills useless.
6. He is not out to destroy Atlantis. As someone with the kind of top-secret clearance and knowledge he possesses, it is very risky to treat him with the callousness and carelessness Weir does. Obviously if he were willing to act in a way that he considered destructive to the mission, he would have great capacity to do so. The fact that he so far has not (in spite of Weir’s ridiculously provocative attacks on his integrity) shows that he has some sense of either loyalty or self-preservation strong enough to make a whole lot of fanon treaments of him completely OOC. Note that, as I think he sincerely considers Weir to be a poor leader, he would not see attempting to get her removed as damaging to the mission.
7. There's no proof he is always a jerk. His personality as shown so far does not tell us much about what he would be like in personal situations. We can’t know that he’s selfish or sneaky or manipulative, etc., just that he has a very strong sense of hierarchy and his own worth. When he becomes hostile toward Weir, it is in direct response to a personal attack she makes upon him. One can extrapolate, but all evils do not correspond to social weakness or unpleasantness. The assumption that he would be cruel to other characters is purely conjectural, and while possible, needn’t be so prevalent.
8. He isn't a loose cannon. We do have reason to believe, however, that he plays by the rules, as he understands them. The acts of vindictiveness he often is engaged with in fan fiction seem to me very OOC. This guy is much more likely to appeal to authority if possible, rather than take his own revenge.
9. Weir's opinion of his performance isn't always right. Kavanagh was right to bring the information to Elizabeth that there was a risk to Atlantis in  pursuing the rescue of Team Sheppard in 38 Minutes. It was her job to gather information and make a decision; his was to provide facts. If he fudged or lied about those facts, she’d have been right to chastise him, but a good leader doesn’t punish subordinates for intel. He tries to do his job, as he sees it, but the fact that his values don’t completely match Weir’s and Sheppard’s doesn’t automatically make him wrong.
10. He isn't a complete coward. There is nothing in canon to prove that he would *not* sacrifice his own life to save the rest of the city, if that became necessary. Granted, there is nothing to prove he would do so, either. But he did join the Atlantis mission, and that took courage. He did not know if he could ever go home again. So he clearly is not completely craven.

All this said, I’m not really a Kavanagh fan. I don’t have a strong like or dislike for him personally, but I do think that folks watching confuse social skills/charisma with ethics and job performance.