In the mail section we have very different indentations and formatting in
texts with sanitize, links and texts with interpolations. In my opinion it
helps a lot to have clearer indentations in these cases.
This may not be the best way to indent them, but at least I think it is
clearer than it was and at least relatively unified.
Using the `_html` suffix in an i18n key is the same as using `html_safe`
on it, which means that translation could potentially be used for XSS
attacks.
