It's like the unofficial but legal way of making your own schedule if you're doing it often. Trust someone will be talking behind your back about it. At some point they may take it in consideration when adding you to the schedule. I've never had to do a write up about it but I have had to do PDDs on it several times.
At my store, as long as someone shows up, I don't think they care. lol
I tried to change my availability and was denied so whatever shifts they give me that I can't work I throw up on the swap shift board.
I think they frown upon it if you are a super star of an employee and get a dud to take your shifts. I know I used to get annoyed that they broke their scheduling promise with me so I found one of the crappy employees who was struggling for hours and got him to take the most crucial of my shifts for about a month until they got the hint. My team leads and ETL tried to fight it but HR said there was nothing they could do as the employee who I was swapping with was trained in my area and if they were that bad of an employee they should have performanced them out.
That being said if no one takes your shift you are still responsible for it. I think the thing people forget is putting a shift on the swap shift board does not excuse you from that shift until someone takes it. Once it is taken and signed off on it is no longer your problem but if no one takes it you still need to show or face the consequences.
At my store not only do we have a swap shift board but have to fill out another form and turn it into HR with our signatures, printed name, and the shifts being swapped....I guess it is to keep track of the people who are switching