Table formatting collapses on pasting

[Durss]

Describe the bug
When pasting formatted table to a formatted table cell, the whole style of the table is reset.

To Reproduce
Steps to reproduce the behavior:

1. Go to this sandbox
2. Tripple click a cell to copy it
3. Paste it to any other cell
4. Styling of the table resets

Expected behavior
The styling should remain.

Screenshots
Here is a before/after pasting top right cell on the bottom right cell:

Here is a diff screenshot of the content before and after:

[JiuqingSong]

OK, I can repro. We need a fix.