It would be the Free Software Foundation, for a copyright violation due to GPL licensing violation. (Technically the Linux Kernel Foundation, as they’re the copyright holders here, but the FSF is generally involved in suits to protect GPL.) It is not necessary to demonstrate damages for copyright infringement; there are statutory (assumed) damages for this tort.

WOULD they? It depends on how important it is to have a credible threat of enforcement for GPL violations. But it’s not zero, and it’s a pretty clear violation. Which is enough to scare off most major distros - if they receive a C&D, that’d be a breaking change they’d have to push retroactively. Not worth the risk.