Hello Sheng-Ta, thanks for replying.

You said:

"This piece of evidence actually works against your favor. If your interpretation is true, then it means that the copyist was aware of the long ending, BUT still chose to copy up to Mark 16:8."

Yes. That is exactly what I said.

You said:

"Why? Why not just copy all the way to 16:20? To cut the book off at v. 8 is very abrupt. There is no reasonable explanation for the copyist to do that unless they thought that the original version of Mark did not contain v. 9-20. They might have left room for other people who think otherwise to add those verses later (it's pure speculation by the way), but the copyist ended the book at v. 8, followed by the title of the work "The Gospel according to Mark". Deal with this implication instead of just brushing it aside."

I already dealt with the implications.

The evidence is clear that the longer ending was already known and held as authoritative at least 150 years before this manuscript was written.

But -- as you've highlighted -- the verses are weird.

They generated controversy within the Christian community then, just as they do, today.

Whoever wrote Vaticanus and Sinaiticus knew of the verses, but chose to leave them off. It's not hard to guess that they did so due to the controversy they generate.