The reason seems Facebook Social Plugin. After I removed it, Comments/Leave a Reply form is back.
I translated the po file (%94) into Turkish, just in case others might need it, which can be found at http://niyaziyarar.com/angular/tr_TR.po
Those are not necessarily to be hr tags, could be css as well. Anyway, another example is 2 consecutive dotted lines under a blog post, which makes too many horizontal lines in a page, really disturbing :(