The online help for vendor credits could use some improvement/clarification.  Just to be clear, I'm talking about credits/discounts here, not vendor returns:

1) I've never understood why creating a vendor credit automatically updates inventory (when items are selected, that is), but in any case I think the online Help should warn people about this.  It doesn't explicitly say that when you have inventory items selected on the Bill Credit form, it will remove that quantity of items from inventory.  Frankly I'm not even sure it's supposed to do this....but that's what it does, and this could really create enormous inventory problems for people if they're not aware of it.  And just to be clear, this happens regardless of how the credit is raised (ie, "Create a credit directly from a vendor bill", "Enter a vendor credit manually" or "Create a credit directly from a vendor return").