"Many, many things are smaller than the Planck constant."
Do we have a proof of that? Honest question. I know strings are often postulated to be smaller (by many orders of magnitude in some cases) but we are not yet particularly confident they exist. I'm not aware of us being reasonably confident that anything is smaller than Planck's size. ("Smaller than Planck's size" isn't even all that easy to define.)
The mass of a blackhole determines the size of the event horizon.
To have an event horizon smaller than the planck constant, the mass have to be also small. While theoretically possible, i don't believe this has ever been considered possible in reality - see https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)
Do we have a proof of that? Honest question. I know strings are often postulated to be smaller (by many orders of magnitude in some cases) but we are not yet particularly confident they exist. I'm not aware of us being reasonably confident that anything is smaller than Planck's size. ("Smaller than Planck's size" isn't even all that easy to define.)