Ah well, then there's the mathematical asterisk operator O∗ (U+2217) which is separate from the ascii asterisk O* and you could also use the "combining asterisk

Ah well, then there's the mathematical asterisk operator O∗ (U+2217) which is separate from the ascii asterisk O* and you could also use the "combining asterisk above" O ⃰ (O, whitespace, combining char) although that's probably abuse of the characters. The rules say > Text surrounded by asterisks is italicized, if the character after the first asterisk isn't whitespace. But apparently noen of the zero-width spaces are not counted as whitespace.