Thought leaders need to stand out.
Bono's glasses, Seth Godin's bald head, Malcolm Gladwell's afro; are part of their brand.
How do you do this?
1. Whatever you choose to use as a signature needs to be congruent with who you are. Choosing to wear cowboy boots and a big buckle will only work if it's who you have been or who you are. Otherwise it's an affectation that's a gimmick.
2. You need to build a constellation of elements, not just one. It's when you put several small ideas together in a constellation that you get a signature style.
3. It's helpful in some way to others. Maybe in only that it helps them remember your key idea or message.