The Testing Done is a bit too long. We need this to wrap around 75 characters so it fits well in a commit message.

The Description needs to be fleshed out a bit. It shoud clearly communicate to anyone reading what the problem was and how it was addressed (without going too far into the nitty-gritty).
You can look at prior commit messages or some of our open review requests for some inspiration, and I recommend reading through our Writing Good Change Descriptions guide.

The Summary is making a statement, but not describing the change particularly. Similar to the description, I recommend reading through our commit or review request history to see the way we describe changes.

Blank line between new selectors.
It'd also help to document this by adding a comment explaining what this is for, so that nobody has to remember or go through commit messages.
Multi-line format for LessCSS files looks like:

/*
 * <text>
 */

There's some extra trailing whitespace that was left over here.

With the rename, the : ... no longer aligns with ? ....

With the rename, these no longer align.

The extra blank line added here should be removed.

Thanks, Akim! Is the hit area still too small, or does this seem to address that somehow?

It might be worth adding a comment just above this block explaining why we're doing this.