I saw this issue today running an unmodified 1.8 client. I was connecting to a vanilla server which makes a big deal out of running the unmodified mojang jar.
Agree with other commenters. I can use this with @p and coordinates to locate any other player on my server. As unknown says, 3 whispers and you can triangulate another user's base.
A simple fix would be to restrict regular players so that they can only use x/y/z/r modifiers in some local area around where they are currently standing. Actually restricting the "r" parameter is the most important to avoid easy exploitation. It would be nice to at the least provide a server flag to allow a server owner to restrict the usage of selectors in some way.
Many of the bugs closed as duplicates also complain of being unable to connect to the server, the log spam being incidental to the report. Does this bug being fixed mean that the log spamming is fixed? Or has the issue mentioned in the duplicate bugs (unable to connect to server, timeout exception displayed) been resolved?
Now that we have the outer End islands, maps in the End would actually be useful. I propose that you consider reopening this bug and providing support for mapping in the End. There are so many islands, all so similar, maps would be nice.