What advice would you give to the mild mannered IT guy who is thinking about gifting his office crush a pedicure gift voucher?

I’d tell him that it’s unlikely she reciprocates his feelings and that even if she does, most people have an attitude of “don’t shit where you eat” so it can’t go anywhere, and that even if somehow she does reciprocate and is willing to actually go places with it it’s likely to go wrong eventually and then work will be awkward and because he’s a guy he’ll probably be labelled as the asshole in the situation.

That is, to say, that it’s okay to offer her a gift but not to act like it means she owes him anything, and to respect it if she says “no thanks”.