There are of course almost as many points of view as there are forum members however my personal point is that - coming from real world aviation and presently working in a company which produces Route Manuals - that it is always a bit confusing as the "automatic" part of my brain is still interpreting an underline as "at or above" (maybe 37 years of active aviation has left me a bit inflexible... ). In addition to that the shorthand for clearance notification (as it still can happen on a few exotic airfield where the whole ATC clearance is given by radio only) also uses exactly the same symbology with either underlined, overlined or both.
So as a conclusion: if there will be a vote I will vote for that
Oskar