[Arrow]

I just tried it on my MBP.

Double clicking on the dynamic HTML note opens it in Safari. All the triangles work.

Double clicking on the OPML note opens and works normally in OO and Circus Ponies Notebook.

Double clicking on the zip file of the OO3 file unzips it in Finder. The native OO3 file is there and double clicking on it opens it in OO and it works fine.

Having the Premium Evernote account may be the key.