The existing mediawiki.ui/components/default/buttons.less has:
// This overrides an underline declaration on a:hover and a:focus in commonElements.css, which the // class alone isn't specific enough to do
a.mw-ui-button { text-decoration: none; }
2. Quiet buttons. I remember clearly from talking to May that we wanted them to be colored in their default state and make them slightly darker in hover.
It's tricky because a row of Cancel Preview [Save] would turn into gray-blue-green multicolor, but without it there's no indication of the button type on mobile.
BTW latest Flow mockups have an "even quieter" design for Reply · Edit
actions before you get a textarea with a quiet Cancel button and a CTA [Reply] button.