On a more substantial note, that's documented here:

https://www.w3.org/TR/2008/WD-html5-20080122/#hyperlink0

It's a little odd, to see that a browser "must parse", but also "may either ignore the ping attribute altogether, or selectively ignore URIs".

It strikes me as a bit clumsy compared to the typical MUST/SHOULD/MAY wording.

Anyone (other than Google) using a-pings?

Ah yeah that's definitely going to be different HTML on Lynx, then, since I bet they don't support that and Google's not missing out on tracking.

Yup - curling with Lynx user agent gets a targets of href="/url?q=<whatever>" rather than href="<whatever>" ping="tracking"

Hm, so now I can go straight to the Google hosted AMP version without bumping through Google an extra time first? /s