It took another several months, but +1 subscribe comments were finally killed without Snowball/Leapfrog/Coordinating-community-initiative's help. I would like to think the Drupal Association blatantly ripped off this idea though :-)

From today's DA newsletter:

We matched community donations to end +1 subscribes. We've all hated the avalanche of +1, sub, and subscribe comments on issue queues around, so we're doing something about it. As part of our continued efforts to make using a great experience, we've matched community donations to solve an issue posted almost 6 years ago! Thanks to everyone who has been working on this, especially Derek Wright. Follow the progress and help with the testing: Let this "+1 Subscribe" be your last.