Can quartz be sealed? If so, would it have beneficial effects?
I'd suggest finding the local stone supplier (possibly through your local kitchen installer), and ask them. 

It sounds like your quartz is more porous than usual is you are getting stains on it - unless you leave wine on it for hours you should normally have time to wipe it up.

Normally quartz benchtops aren't very porous, and so don't take up spilled liquids. This also means they don't take up sealant very well. Maybe your bench will take a sealant since it is more absorbent, but you'd be better talking to someone who can inspect your bench first, or even knows the quarry your stone came from.

I wouldn't expect sealing the bench to be harmful, if using usual stone sealing products.