WowAce

When control + click [Questionable Meat] to send similar items [Jeweler's Kit] keeps being added aswell

Basically a won't fix for this one.

The feature is using a Blizzard API GetItemInfo to return information about the item you control + click on vs. other items in your inventory.  The compare design in Postal makes a best guess for matching/similar items by looking at are identical, are vendor trash, are BOE, are the same type, or the same subtype, or the same quality.  In this case Blizzard API returns that [Questionable Meat] and [Jeweler's Kit] are of the same type so we consider that similar enough.