I don't think I've ever looked at someone and thought they were silly for wearing a suit. My company is smart casual dress code and we have people come in with suits on all the time
Then they're clearly not out of place, in fact in plenty of places with a "smart casual" dress code you'd still find employees wearing suits from time to time, especially when meeting clients etc..
The point was a general one in relation to people getting stuck in the mindset of "always wear a suit" even when it is clear it isn't required - see the mixed response to this guy's query for example:
https://forums.overclockers.co.uk/posts/32133163/
in theory an interviewer probably shouldn't place too much emphasis on it regardless - whether you turn up casually or suited and booted, it is your performance at interview that counts but some people will form some subjective opinion based on it and you're trying to build up some rapport in the interview - I'd not turn up for an interview at some big investment bank wearing say a polo shirt and jeans and likewise at some new tech start up where I've been told already that there is no need for a suit I'd not then turn around and ignore the information given and turn up wearing one
If it hasn't been made clear or isn't obvious then of course a suit is probably the safer way to go, that ought to be obvious, in your case in a regular office environment with a "smart casual" dress code (by which I'm assuming collared shirt + smart jeans or trousers) I'd wear one but that isn't what I'm referring to but rather the attitude that it is always the answer in spite of evidence to the contrary, which is what seemed to motivate some replies in the other thread. Anyway I hope that clarifies, my initial comment on the matter was intended previously to just be an aside on the general attitude to suits I don't really want to take the thread off topic by having an ongoing discussion about interview attire.