Thank you.
I haven’t found specific researchers about text legibility in VR.
On your place, I would take all concepts about the legibility of 2d text and tried to find aspects that VR might affect.
Another thing is 3d fonts. Theoretically, it’s a good idea of having 3d text in a 3d environment, but practically we feel that 3d text is less readable and legible. It can also be exciting research.
Please let me know what you’ll find out.