the comments panel synced with Lr Mobile is a great new feature in 5.7.
Do anyone knows whether comments and likes are searchable in Lr?
I could not find them in filters and in the Smart Collection panel, though it would be really useful to have them part of a smart collection (to filter commented photos).
No, the comments (which are also synced with services like Flickr) are not searchable -- you can't even copy and paste from them. And they're not accessible to plugins either, unfortunately. Seems like a half-finished product idea.