ㄴ다는데

They say, and about that

It passes on what people say and leaves the sentence open for your reaction or a follow-up question: they say you get milder as you get older; apparently not even dogs catch summer colds; I hear I can call you when the road is jammed. The open ending is doing real work, since most of these lines are caption teasers that set up whatever comes next.

Register: everyday; very common in captions