I can't figure out how to get real use out of the comments and favorite features with a large collection on lightroom mobile. For example, I have a collection synced with 400 images. My collaborators have been told to mark them as favorites and to use comments if necessary to make choices clear. But the only way I can use the favorite markings is by going through the collection one by one and maybe then color labeling them so I can create a smart collection of favorites or even a smart collection based on the content of comments. This is a major pain in the neck.
Unfortunately, you can't search/filter for comments or likes. The best you can do is to sort a synced collection by Last Comment Time, which will sort all the photos by the last time they were commented / liked.
Please add your vote and opinion to this topic in the official Adobe feedback forum, to make it more likely Adobe will prioritize a fix: Lightroom: Better support for comments and likes, in ALL publish services