[UX] Refreshless doesn't give any indication of fragments of a page being loaded on slow page loads

The module works great in my testing, but there's one test scenario in which I got confused. When you have slow page loads, refreshless makes you think you've either not actually clicked on the link or it's broken...until the page 'fragment' actually gets loaded, eventually.

I wonder what could be done to improve UX here? Would a discrete spinner somewhere would be too intrusive?