Hot shoe and PC terminal max. voltage

The 50D manual says:


1. "Do not connect to the camera's PC terminal any flash unit requiring 250V or more."


2. "Do not attach a high-voltage flash unit on the camera's hot shoe. It might not fire."





So, is it safe to connect my old flash (which has a triggering voltage of about 230V)?


Why the hell Canon can't just tell us exactly what can be connected to the camera? what's considered as "high-voltage"? 2V? 94V? 6734V? why can't they just tell us the exact specifications?


and... "it might not fire"... will it damage the camera or just won't fire? [^o)]