1) Cannot be converted by one party alone; both parties (company and shareholder) must agree. 2) Can never be converted no matter what happens.
#1 is correct and #2 isn't, but some like to conflate the two definitions for some reason.
Mark Calabria specifically mentioned the possibility of a junior-to-common conversion. He's not stupid. If it was either illegal or unworkable he wouldn't have said anything about it.