Doesn't being under $HOME make .local redundant? I guess one could argue for binaries going in an architecture-specific subdirectory if $HOME was on a shared filesystem, but that's not what's being done here.
To me, $HOME/.local/share and its siblings are just a needless level of indirection, forcing me to jump through an extra hoop every time I want to access what's in there.
(I know it's sometimes possible to override it with an environment variable, but the predictably spotty support for those overrides means I would then have to look for things in two places. I think sensible defaults would be nicer.)