Hi Luca, so I found out some more information.

There are actually 2 different varieties of .otf font files - one variety has "TrueType Outlines", and the other variety has "PostScript Outlines".

The "TrueType Outlines" type of .otf file should work currently in MoI v1 and v2.

The "PostScript Outlines" type of .otf file will not currently work in MoI v1 or v2, but I think that I have got this fixed up so that MoI v3 should be able to use them.

- Michael