I think the problem is everyone is not seeing what the other is doing. Melon is not lunging, he is changing foot position from a 5-6 to a 1-2 and doing a vertical slash.  He is not lunging at you and you made a terrible mistake in your response. 

Sath, if you are doing medieval fencing you know what I am saying here, you should have waited and [i]in des fechten[/i] or[i] gleich fechten [/i] to take advantage of his action. With either a counter thrust or [i]Uberlauffen[/i]. 

You did deflect his attack with a diagonal attack on his blade, but you didn’t follow it up with a cut over the blade, which you should have done since it would have been a natural action following the movements you and he engaged in.