We already know that we're not retarded and that's why we find it annoying cause some us are not little kids and can actually entail that meaning of something in less words.
You can still say more. It's not about just having one little pithy statement and then moving on. 100 characters is a tiny amount. It's not that hard to come up with enough to say. And you should know that better than I would, being thirty-six to my twenty-five.