I found the culprit of tile overlapping today. It was the global footer. And the next one is recent posts I used in Sidebar. It was showing that there is no post in last day, week and month. Also I am still not able to feature the posts.
There seems to be some kind of mismatch here. I'm watching two categories (General and Development); there's a "1 unread topic" bubble, but when I go to https://community.nodebb.org/unread, I get a "no unread topics" message.
Probably a very small error somewhere, but worthy of correcting.
It's gone away on its own after posting this thread -- but it shouldn't have been in that state to begin with, right?