Per @jorge_manrubia this is now implemented. I pushed the change here:
https://github.com/discourse/discourse/commit/86d12bd44bb23767958364743a2afdf064331c81
Note: the UI is not updated yet, we are going to wait a few betas.
Keep in mind, this change will slowly appear on your forum after the update. We will update the search index for 20k posts every 2 hours to gain the new feature. If you feel like rushing it:
./launcher enter app
rake search:reindex
A rushed reindex is running on meta right now.