Problem
Canceling a render is so easy a cat can do it by walking on a keyboard and stepping on ESC. For long renders, especially with Cycles, accidental cancellation can waste a lot of time.
Solution
A simple dialog prompt (like deleting an object) could help prevent this without being too obtrusive.
Lol. I don’t think this example accomplished what you thought it would.
I don’t know what you mean.
What i meant was that most people would consider the likelihood of a cat stepping on one single unique key on a keyboard with 101 keys on it, to be quite low.
So, as an example, it doesn’t serve to support your argument that cancelling a render is a very easy thing to do 
I’m not trying to persuade developers. I merely saw a post on BA making a complaint about it and figured I’d throw a suggestion in the suggestion box. The devs will either change it or they won’t.
The cat part is a true story.
I’d want this, if only to have the feedback that my cancel request has been received by blender (or that it isn’t being received / is waiting etc).
Just saying that I wouldn’t want this. If my machine is rendering, my interface is loggy. I’d rather just wait for the ESC key to register than wait for it to register, wait for it draw the popup, wait for the click on the pop up to register, etc. I prefer Blender’s responsiveness to other rendering experiences for this reason.
But that’s just my vote, worth no more than anyone else’s. I’d simply prefer a “resume” or “continue” feature for progressive renders.
Seems like a really great idea, but ideally the user could decide in userprefs if they wanted it or not