If you want to find documents that has a comment with title = "Comment 1" then you can use :
db.test.find({"comments.title" : "Comment 1"})
If you also want to project result so that it only shows subdocument, then you should update query as follows :
db.test.find({"comments.title" : "Comment 1"},{comments : {$elemMatch : {title:"Comment 1"}}})