Talk:Thornmail/@comment-82.236.121.171-20111004220029/@comment-76.21.69.1-20111007010900

"Thornmail reflects both physical and magic damage; the only determining factor in its trigger is whether the attack is defined as proccing on-hit effects. For example, Warwick's  Infinite Duress deals only magic damage, but still procs Thornmail's Unique Passive."

Vayne's silver bolts don't trigger on hit effects, technically, so I don't think so.