You seem to have a lot of questions regarding stabbing, knifes, rapiers, belly wounds... Maybe get some martial arts or self-defense expert and ask them! Generally you'd find them in some club or sports event and less so in random corners of the internet.
If you're 6'6" you're in for a lot of stupid questions and statements. How's the weather up there... Do you play basketball... How tall are you... Wow, you're tall... And a myriad of other silly comments. I guess this is just one of those conversation starters.
Usually these don't make sense. But are some form of compliment, an (awkward) way to get a conversation going, etc.
I'd say the proper way to defend against a knife attack to your belly is either have a massive belly so the blade can't reach your organs, or bring a gun and shoot them first. Or do it like Crocodile Dundee. Or just run away. All of that can be done at any body height.