Interesting. If it's because they're harder and more confusing than other solutions, that's unfortunate they would respond they way they did. Especially because, if you follow the link to what "discouraged" means, it says:

"From time to time, we may mark language constructs and features which we consider to have been mistakes as discouraged. Discouraged features aren't currently candidates for removal, but we may later deprecate them if they're found to stand in the way of a significant improvement to the Perl core.

When I read that, it sounded to me like threads were possibly going to be making an exit from perl. If they had said "look...these are hard to do well," it could have saved me a lot of confusion and running around. I think I also don't understand why the time and energy that goes into that whole process of getting that into the documentation doesn't go to better informing and teaching others the best/right way to use them if they are, in fact, often the better solution. But I guess that's a philosophical difference.