David Nebenzahl wrote:
One of my customers has a weird thing on one of their hose bibs outside:
a large brass or bronze cylinder with male hose threads outboard
(presumably female on the other side), and a series of holes around the
male threads. As the customer put it, it seems to be designed to ... let
water leak out, which is what it does when you use the hose.

They surmised that maybe it was put there to guard against overpressure.
I've never seen such a thing.

Anyone know what this might be,

Anti-siphon hose bib.

and whether I can safely just remove it?

Most likely required by code. It sounds like it needs fixing or
replacement if it's leaking continuously.