LibertyBelle....
I don't think you're being preachy at all. I understand exactly what you are saying. If someone is trying to find a way to sneak a child that is 2 inches too short onto a ride, then I absolutely agree with you. If someone is trying to find a subtle way to get a 39 3/4 in child onto a 40 in ride, then I think that's different. I don't see the harm in buying a sneaker that has a slightly thicker sole (BTW ...to the OP. They have cute sneakers at Target with a thick sole). We're not talking about elevator lifts here. I doubt the height restrictions are so percise that Disney set it at 40 inches because 1/4 inch shorter would be unsafe.
I'm not trying to encourage dishonesty. When my family bought our AP's my youngest was 2. The next time we went, she were 3 and I bought her AP (and she would have easily passed as 2) as well as all her food. I don't think these 2 issues are the same though. When my DD was an inch too short, we told her she would have to wait. When she was 1/4 inch too short, I compared sneakers/height. I didn't buy her platform shoes or anything...just a regular pair of sneakers with a slightly larger sole. Disney was free to measure my 39 3/4 inch child. If they had asked her to take her shoes off, I would not have argued the point at all. But, truthfully, they never even asked to measure her the whole time we were on our last trip. I cannot imagine the CM's were able to look at her and think "She's definately 40 inches." Yet she was never measured.
To the OP: I definately wouldn't push beyond 1/2 inch (if that). There are safety issues and they shouldn't be ignored. If you are just trying to get over that last 1/4 inch, then look for good sneakers.
Jess