gqap results in "par error: Impossibility #5 has occurred. Please report it."

[mingyuguo]

How to reproduce this bug:

Linux, create a document without extension.
Fill in random Chinese paragraphs (Chinese characters in unicode take two slots instead of one)
use gqap, I get the error in the title, and the paragraph is completely gone.

[mingyuguo]

After some googling, I disabled "use par for prettier line formatting" in .vimrc

In my opinion, this default option is pretty dangerous, because it empties out the paragraph it tries to format.

[begriffs]

What's a better formatting program we should use?

[mingyuguo]

I have no idea. vim default seems fine.