WP.com offers full justification for text. While the feature will always behave as expected in the editor, it will not always display properly on the front-end.

This is due to faulty logic while enqueuing common.css – fix is in D34065-code.
This is due to faulty logic while enqueuing
common.css– fix is in D34065-code.
Is this the same issue as https://github.com/Automattic/wp-calypso/issues/36770?
Yes - I'll close that one. :)
Fixed in D34065-code.