Hi. Someone has advised that you cannot use the mic socket when recording in High-Def. Can you confirm if this is the case? It doesn't sound right. Thanks

You can use either the built in internal mic, or an external XLR mic in all shooting formats. You just can't use both at the same time (for example, you can't use the internal on channel 1, and XLR on channel 2 at the same time).

Basically, your info is false.

Ditto everything Vito has said.
What else did they advise you? I'd love to be a fly on the wall there. HeeHee.