The <a ping> attribute could be used to increment the counter.
Caveats:
- It’s disabled by default in Firefox.
- there don’t seem to be any JS events for it, so the counter would only visibly be updated the next time the post was visited.
NB: It seems like “mousedown” events are triggered on middle click, but that would have false positives as not every click ends up being a navigation - eg. copy link, customised browser settings.