Howdy,
I’ve been working on a package to fix syntax highlighting for Less. Most available packages for editors aren’t current with even CSS3, let alone Less 2.7 (most were converted from a 4-year old tmbundle, then modified to add a few pieces here and there).
With regards to CSS grammars, Sublime Text 3’s is the most up-to-date. Since the sublime-syntax YAML format isn’t directly compatible with other editors, the long-term goal is to have up-to-date Less syntax highlighting for TextMate, Sublime Text 3, and Atom, and my first step is to get it working in Sublime Text via the YAML-tmLanguage format and PackageDev.
This project is still in its infancy, and pull requests/feedback/criticism/ideas/cookies are appreciated. I’ll likely submit it to Package Control once I feel all of the important parts of Less are fully covered.
Thanks!