I felt that Ron Moore did
ruin the Bashir character by making him genetically enhanced. Mainly because it turned out to be DS9's biggest continuity error. There were certainly no hints from what we've seen from the previous episodes mentioned let alone anytime in the show's earlier seasons. Julian was so boastful about himself in the first season, which is something he's not supposed to be doing if he were hiding such a secret. And it definitely should have been mentioned in "Distant Voices". If I were a telepathic killer alien, I'd certainly use something like that to my advantage. Another sign of the continuity error would be with Julian's little teddy bear Kukulaka. In "The Quickening", he said he was able to sew and patch him up when he was 5 years old. But if were extremely deficient at that age (saying he was enhanced around his 7th birthday), he definitely would have no such capability.
The continuity issue is debatable, but if you think about it, we should have gotten some hints from the early seasons. This earliest possibility should have been in S1's "Q-Less". A being as omnipotent as Q definitely would have known the secret, since he said he knows everything to Vash's annoyance in that episode.. In the scene he induces Julian to sleep, he says quietly to himself as he leaves the restaurant "Hopefully by yourself for a change". The writers could have added another line afterward like "You're still inferior to the likes of me no matter what they did to you". Something like that would have first-time viewers wondering what the heck he was talking about. An obscure line like that would have a significant role in what we would learn later about Bashir. But the fact is Ron Moore blew it big time by adding something that big about the character so late in the series.