Are trouser braces really esoteric enough to provoke that reaction? As long as you're wearing a jacket they're not especially noticeable.
My experience would be no, though I'm informed that e.g. brown shoes are seen as Bad in finance - not a fact I'll ever have cause to worry about naturally - so Lord knows wrt some workplaces.
Basically the same scenario - generally speaking, if someone in an entry level position in financial services (or applying for one) wears braces it's assumed (often with good reason) that they've watched Wall Street too many times and think they're Real Life Gordon Gekko. Given that the whole point of being in an entry level position is to do the sh**tty jobs and not to draw negative attention to oneself, wearing braces is not advantageous (as with brown shoes, dodgy haircuts, pinstripes and the like). Now, whilst I wasn't around for when braces were in vogue, I do rather like the aesthetic they bring. On the other hand, I'd also like to present as narrow a target as possible, so I'll pack it in until such a time as I don't have to worry (as much) about how my sartorial choices are perceived.
Also on the jacket business, that is a fair point, but on the other hand offices can get pretty sweaty (especially if the cooling is poor/non existent or you're positioned in an awkward spot getting hit by the sun full blast), and jackets are pretty cumbersome things to sit/work in.
Ofc, this is just
my personal experience and knowledge, but it is what it is.