This is a usability suggestion.
Every time you buy an item on the auction market, you get a message.
Now, there are 4 cases:
1. You got an item when its timer expired, but didn't have room for it
2. You got an item when its timer expired, and had room for it
3. You bought an item with "buy now" but didn't have room for it
4. You bought an it with "buy now", and had room for it
In cases 1 and 3, you obviously need a message that the item is in your Cache rather than in the backpack. In case 2, you also need a message, otherwise you might not notice that you got the item. But in case 4, a message is obsolete and annoying - I'm aware I bought the item, I just clicked on "buy now", didn't I? So a message just forces me to go read something I already necessarily know.
My suggestion: Only generate "item bought" message for "buy now" if the item went to the cache and not to the backpack.
