Confirmed — the Pet Name Tag genuinely does nothing when you use it.

The renaming machinery is all there and working (name length limit, the floating name plate above the pet, saving the name across logins), but nothing was ever wired from the item to it. The tag falls into the "cash" item category, which the use handler rejects outright, so a double-click was a no-op with no message. The only way to rename a pet right now is a chat command, which no player would know about.

The patch hooks the item up: using it with a pet out opens a name box, applies the name, and consumes the tag. Using it with no pet summoned will say so and keep your tag instead of eating it.

While I was in there I noted the same gap on the Pet Label Ring and Pet Quote Ring — those do fit into the pet window, but I'll double-check they actually change anything once fitted.

Confirmed — the tag really did nothing. It lives in the Cash tab, and the inventory window only sends Use / Set-up items plus a short hand-written list of special cash items down the "use" path; the name tag wasn't on that list, and there was no naming prompt anywhere in the game (only a chat command). Double-clicking or right-clicking a Pet Name Tag now opens a small box asking for the name, renames the pet you have out, and spends the tag only when the rename actually happens — cancelling or closing the box keeps it. The box caps the name at 12 characters, which is v83's own limit. If you have no pet summoned it says so and leaves the tag alone, rather than burning it on nothing.