I interpret this as suggesting that #3 is the correct cause; am I right, or do you mean something else?

"The correct" is too strong; I was shooting more for "a plausible." But it is mostly 3, but I don't think 3 and 1 are exclusive. If esse quam videri is a neat thing for other people to think about you, then it's worthwhile thing to signal! (I found amusing that one of the first Google Image Search results was of a tattoo of the phrase.)

My impression is that one has to do some sort of signalling, and you seem to have the same impression. It seems to me that doing it deliberately is probably better- especially if the result is deliberate white-hat signalling rather than only doing the black-hat signalling that you fail to notice is signalling.