Except that % is already used to encode something else.
Now if someone else a URI, is there going to be any confusion on how many times a URI needs to be decoded?
If the answer is yes, then we have a problem.
(and by looking at the other comments in this thread, the answer is most definitely yes)
It only needs to be decoded once? The raw % is in the host and will be recovered by this process. Same as any other url encode/decide situation