Just a random thought from a novice: We season pretty much everything with salt to make the flavors pop. Why don't we salt things like balsamic vinegar or wine reductions, or even something like a buerre blanc? Or does everyone else do this while I remain in my own little world?
Any tips on what types of sauces to salt?
For most of the dishes I prepare, there is enough salt in the dish itself and the sauce doesn't usually need to be salted. It is, after all, simply a condiment that enhances the flavor of the dish and not the dominant flavor ingredient. I believe you should always taste what your prepare before serving it and, if you taste your sauce and are convinced that it needs to be salted there is no reason why you can't add a pinch - but it's something I rarely add.
Maybe other people do salt those sauces, but I think those flavors are intense enough that they don't require - uh - intensification. Which is what salt theoretically does, right? Bring out the flavors?
I've actually read that the liberal use of acids in particular - vinegar, lemon juice - is an excellent way to make low-sodium food palatable.