Thanks, I think this is an improvement.

Before

After

And

Here's a GitHub diff:

Similarly, I think we should keep the lines a bit tighter together.

Here's the PR with the vertical padding removed:

Shall we remove that padding?

And shall we centre the table on the page?

Similarly, I think we should keep the lines a bit tighter together.
Here's the PR with the vertical padding removed:

It's a good improvement, and this is what it looks like now

And shall we centre the table on the page?

I before thought about this, but the table width is determined based on the length of the content and the code specified, like

             '<h2>tabsize=2</h2>',
             j.make_table(f2,t2),
             '<h2>tabsize=default</h2>',

If we center the table, there will be a lot of space on both sides of the screen, and it may not be as easy to distinguish as if the table is narrow. So I didn't do that, and my opinion is also to keep the left alignment the way :)