Update:
I took a closer look at the key that broke the Tor key with its signature:
pub rsa4096/4F3F50786C401DCE 2015-10-04 [SC] 17F9D6D43CE4DDEE4178548C4F3F50786C401DCE uid Richie ryetschye@web.de uid Richie ryetschye@posteo.ru uid Richie ryetschye@ironcomputing.de uid Richie (IRONCOMPUTING) richie@ironcomputing.de uid Richie (IRONCOMPUTING) richie@irconcomputing.de uid Richie richard.gottschalk@stud.uni-regensburg.de uid Richie (IronComputing KG) richie@ironcomputing.de uid Do not use SKS keyserver sites (no validity checks) <@> uid Do not use SKS keyserver sites (no validity checks) https://bitbucket.org/skskeyserver/sks-keyserver/issues/41
Apparently, someone wants to turn people's attention to this ticket:
https://bitbucket.org/skskeyserver/sks-keyserver/issues/41
Although the more apropriate ticket to link to in this case would be this one:
https://bitbucket.org/skskeyserver/sks-keyserver/issues/57
The problem is basically that anyone can dump a whole bunch of data into the UID field of their key and upload it, which overloads both the keyservers and the PGP clients. I've already sent a mail to Kristian Fiskerstrand (the developer of SKS keyserver), explaining the problem.