Does a pinch berry get consumed if you have max boosts in a stat (ie: Belly Drum + Liechi)? This matters because of Berserk in Gen 7 (also the ability to re-activate the Pinch berry after losing a stat level). If the berry exists someone could still steal it or it could be flung.
No, it doesn't. +6 Pokemon doesn't eat the berry until it next comes in under the threshold for its activation, or it loses a speed boost when under the threshold. Tested with a Volcarona and a Salac Berry in ORAS.
I doubt I'll be able to test it in Gen 3, due to how difficult it is to get pinch berries in Gen 3. I'll look into Gens 4 and 5 after I've slept, assuming no one else does it in the meantime. EDIT: I've been unable to test it in Gen 5 due to a lack of pinch berries, but I have tested it in Gen 4. It works exactly the same as it does in Gen 6. As such, I'd speculate that it works the same across all the Generations.