Ugh, it should be `reNotBlank` — I’ve just fixed that.

We can’t collapse all blank text nodes because it could modify the layout; e.g. with this markup, the two buttons would be sticked next to each other instead of keeping the natural separation.
```html
<p data-l10n-id="message"> message <button>[+]</button> <button>[-]</button> </p>
```