User blog comment:DaNASCAT/Technical Update: March 17, 2015/@comment-1251315-20150318113811/@comment-452-20150319225345

Incidentally, you can get around it by renaming your scripts from .js to .javascript since importarticles doesn't care about the extension.

I did this briefly when they stopped loading site+user CSS+JS for .js pages, until I figured out a workaround.