Hi friends,
Recently we've merged in Gather a patch so that the extension uses precompiled templates ( Custom TemplateParser for MobileFrontend and Gather https://phabricator.wikimedia.org/T102941 ) because of a bug in HHVMs closure creation ( https://phabricator.wikimedia.org/T102937 ).
Once hhvm is patched and running everywhere we feel like it is safer to keep precompiled templates on Gather since the extension makes fair use of templates sharing them between the server and js client code.
If you are developing or plan to develop patches for the Gather extension be sure to include $wgGatherRecompileTemplate = true in LocalSettings.php or equivalent during development. That way templates will be recompiled and written to disk every time you visit the page that renders them, so that you can submit them with your patches.
We'll keep an eye on the tracking bug and remove this when it is safe (it is a bit cumbersome, but the best solution considering the tradeoffs right now).
I've updated the Extension:Gather page and added the information ( https://www.mediawiki.org/wiki/Extension:Gather#Development).
Cheers.