I am making radial gridline bubbles. When naming them, I come to “rM” but for whatever reason, Rhino will hide the capital M. Lower-case “rm” is fine. Upper case “rM”, “r M”, “r M asldkfasdf”, “r Masldkjasdklf”, “rMasiodjfasdf” all hide the capital M.
This was some type of corruption of the text in Rhino. All my capital "M"s had disappeared. Closing and restarting Rhino fixed it. No idea what happened.