Shelack or other coating on some briar?

Yes. Some pipes have a clear coat of varnish or shellac. Personally I don't care for them. It can be removed with acetone or finger nail polish remover.

I have one or two of those high gloss pipes, and at least one of them smokes well with that finish. It's a Jobey straight billiard with spot carving, a really snappy looking pipe with an unusual screw-on stem that actually screws in place correctly. Not my favorite design or finish, but a good pipe despite me. Mostly, I buy pipes with less glossy finishes.

Many carvers (including artisan) use a form of shellac, but cut with large amount of denatured alcohol. This is used to set the stain so that it doesn't come off on your fingers when you smoke the pipe. It does add luster. However, depending on if we are talking machine made factory pipes or hand made individual pipes, the degree of shellac thickness can vary greatly.
As long as the coating is thin and diluted when applied, it should not affect the "pores" or "breathability" of the pipe as some would call it. Some factory pipes I've seen have such a thick coating of "varnish" it can be peeled off or flaked like has been mentioned above.
In my experience, if you want a glass finish, you need to use a bit more shellac, but still diluted at least 50/50 with DA. For the pipe with a matte finish, there is probably still a thin coating of the shellac/DA solution, but it is not finished with wax to such a degree as the glassy look.

I respect Clicks experience here so my comment is just personal preference. I want a pipe to breathe and dry out as quickly as possible. A raw unfinished pipe would do the the best but even those will darken over time and fill with oil from the hands. When I get and estate pipe I almost always do something to remove any surface coating what ever it is first. I will use raw carnauba wax to shine it and over time apply more as it wears off. My goal again is to have the pipe breathe and dry out as effectively as possible. Looks is a secondary concern.

I've removed the super-shiny, bulletproof gloss coating from all of my smooth Grabows. I like them much, much better that way.

Shellac is fine, its usually highly diluted and is basically a spit coat. Go ahead ad do it.