Sorry, but I am with Debs on this one. It's not what YOU think is fine - it's honoring the 'done thing'
I totally agree. It's one thing
choosing to tip somebody who is not in a 'tipped position', such as housekeeping, reception staff etc. To me, it's entirely another thing
choosing not to tip somebody who is
being taxed as if they had received the tip. If you don't tip that person,
they are taking a pay cut!
That said, I have never had poor service at WDW. However, I would never leave nothing and here's why:
If you want to get your point across that the service is bad, leaving half a tip speaks a lot louder than leaving no tip (where the server may think that you had forgotten).
An excellent point. If you leave no tip, how is that making your point about the level of service you received

It could be that the server merely thinks you forgot. Yes, they lose out on the money but it leaves them with a poor impression of you, the customer.
On a few (out of 10 visits) occasions (mainly outside of WDW) I have received disappointing service but not bad in that the server was rude or complacent, just more that they were a little disorganised or got an order wrong. To me, that is not bad service - everyone has their off days - and I have never felt that I have not wanted to leave a tip at all. On those occasions, I left a little over 10% - that was my way of telling the server that the service they had provided me with was under par. To be honest, compared with most places in the UK, the level of service received in WDW or other restaurants in Florida is outstanding.
I rarely voice my displeasure at less than stellar service because the British reserve kicks in and I don't like the thought of conflict or confrontation. However if I truly received such poor service that I felt like not leaving a tip or if a server was rude to me, I would have no hesitation in asking to speak with a manager.