> The data isn't available when the handler is bound?

Exactly.

> Isn't the handler bound when the anchor is created? Aren't we creating the anchor because we already have an annotation?

We have **one** annotation, yes, but the several other annotations can also overlap this one, and so be relevant to the mouse event. [This is the code](https://github.com/hypothesis/h/blob/1118-multiple-selections-3/h/lib/_annotator_mapsrc/src/plugin/texthighlights.coffee#L26) to collect all the impacted annotations; that can't be done before the actual mouse click. (Because other anchors/highlights might have been created later on, after this code runs.)