Should I shave my beard if I am currently a civilian but have an interview for a Reserve position?

Maj Matt Hylton Sir, shave the beard.

I joined the reserves with a full beard. There's no reason to shave until at least after you are accepted.

yes! one should strive to look as professional as possible for any interview. Not saying that facial hair presents an opposite effect, but "you only get one chance to make a first impression". If you're going for a potential military affiliated position, cut it off. its only hair and will grow back in time.

Yes

The very questions infers one might be right and one might be a liability in the interview process. I'm certain being well shaved can't be wrong.

Yes. Because you know the rules. It probably wouldn't be held against a non prior as much, but you would be expected to appear in regs.

As said before, dress and groom for the job that you want.

Damn straight!