See T141922#2578626 for context.
With hovercards enabled and the experiment enabled, users in the control group (previews OFF) when hovering a link multiple times and then clicking it will submit multiple click events.
In the hovercards OFF case, when the user clicks a link that has been hovered multiple times, then multiple click events are logged with different linkInteractionTokens. Events have a decreasing totalInteractionTime, e.g. in the automated tests that were run we saw one event with a totalInteractionTime on the order of 100ms and one on the order of 10ms (in real data this will depend on the user's actions and their timing).
When preview is disabled a click event is bound in every hover that is never unbound, which doesn't happen when preview is enabled. As @phuedx mentioned in T141922#2574587, binding click events follows different code paths for the OFF and ON groups.
- Click event bound in every hover when hovercards disabled: https://github.com/wikimedia/mediawiki-extensions-Popups/blob/master/resources/ext.popups.targets/desktopTarget.js#L158-L162
- Contrast with off+bind in every hover when hovercards enabled: https://github.com/wikimedia/mediawiki-extensions-Popups/blob/master/resources/ext.popups.renderer/desktopRenderer.js#L118
- When hovercards is enabled but I'm in the control group (previews disabled), when hovering a link multiple times and then clicking it only one click event will be sent to analytics about that link I clicked.