Quote Originally Posted by Kastion2000 View Post
Does this symbol -- https://bit.ly/3oiFGK6 --- on an item mean it is in use by a particular Gear Set (AKA Class) and if I take that item out of Armory and sell it I will end up with some Classes having empty gear slots?
Yes.

Quote Originally Posted by Kastion2000 View Post
On the same note does that mean I can remove items from the Armory and sell them if they don't have that icon in the corner of the item image?
You can sell all gear not marked as unsellable. It will say if it is on the top of the item text box as well as in the lower left corner.
It being in a gear set is irrelevant to if you can sell it or not.