I can guess the possible reason, some font does not have bold, or bold not installed, or its bold style does not detected by default (objective c) font API.
I know this is true in
*emphasis* (italic style), so I add some extra protection on emphasis. However, I thought bold would be always detected. Probably I am wrong. I have to add same emphasis handling on bold as well...
Can you confirm,
*emphasis* conversion is working or not in same font?