There is an inventory issue that has been present in the engine since Oblivion relating to the ease with which you can sell equipped/ favourited items.

It would be nice if worn and favourite items were locked out from being sellable at vendors.?

Yes, I even prefixed my apparels and weapons with my name to prevent me from doing that and I still managed to accidentally sell them.

Or movable in any way.

The accidental sale i can see as a more corner case issue. The more common qualoty of life impact is every time i want to trade items with my companion, i have only two choices - trade all, or trade one at a time.

There isnt even an option to trade all junk, trade all apparel, etc at the category level. So when using companions to store loot, you end up using the trade all command - then manually give back your companion weapons, gear, and ammo. Or trade one item at a time which is awful if you have long list of loot.

So a lock command to prevent sell or trade would allow trading mass items at once with companions while letting you lock their weapons and gear in place.