Is limiting About Section text input more beneficial or annoying?

Background: According to the study below (Found on NN), users read less than 1/4th of all text on a given webpage. So, theoretically, organizations would benefit from having much shorter about sections on social media sites and the like.

Question: Would having such limitations be helpful or annoying for the users inputting said information? They say good design is invisible, but I feel like limiting users in the way without providing justification could be problematic.

Possible Solution?: Would adding some explanation text in the form of a question mark/info icon + tooltip combo be worth it? Or is it still irritating for the user?

Study: http://doi.acm.org/10.1145/1326561.1326566