Is it normal for brake fluid to leak out on threads of the nipple during a bleeding the brakes? Here's a video

 

Yes if you loosen it to much.
make sure its correct thread and compare angle at bottom with old one.
if ok,
after tightening stand on brake pedal and get someone to watch for leaks.

 

Yes. The seal provided by the bleeder is its angled seat at its base. As soon as its loosened, the fluid is free to work past the threads. The threads are no match for hydraulic pressure.

Loosening the bleeder too much can actually work against your bleeding efforts, if using the pump pedal method, as it can suck air back into the system through the threads.

Speed bleeders, a bleeder nipple with a built in check valve, come with thread sealant applied for this very reason.

If you do gravity bleed, you don't have to worry about the threads.