I'm not sure this is an enhancement.

This is not a human-readable comment as above lines, but a commented out sample. Currently you need to press DEL only once for switching it on. With your changes you will need to press DEL twice, and it will be harder to distinguish it from the above comment.

I agree.

Trailing comma makes the dict easier for modification.

and hence is considered good practice.

Trailing comma makes the list easier for modification.

And I'm not sure that writing 5-tuple vertically adds readability (especially if add yet few 5-tuples) .

What is the purpose of this change?

I presume to have a closing ')' that lines up with 'usage' and 'try', as in some C styles with '}'. But unneeded (...) around Python expressions is not typical style.

Going to change this back to the original which I agree is cleaner.

Multiline strings are one of the two places in the Python grammar where significant indentation is broken. Black tries to avoid unnecessary parentheses but is easily fooled with multiline strings that aren't aligned with the current indentation level. This is a technical limitation more than conscious design.

I agree.

and hence is considered good practice.

I presume to have a closing ')' that lines up with 'usage' and 'try', as in some C styles with '}'. But unneeded (...) around Python expressions is not typical style.

I would rewrite number > 1 and 's' or '' as 's' if number > 1 else ''.

I agree 👍

It is worth to add a space before %.

Trailing comma has a value when the list is aligned vertically (and the trailing comma is followed by a newline instead of ]). You can easy comment out or copy-and-edit the last line by pressing just a few keys in many editors. But if the list is written in a single line, the trailing comma rather looks distractive to me.

Any reason to keep the u prefix around, especially since it's only used on some of the strings?
I would also put the square brackets and parentheses on the same line (i.e. [( and )]) and remove a level of indentation.

Black doesn't hug multiple levels of brackets to make it trivial to scan logical nesting levels visually.

The main issue is the fact that 3 lines are "wasted" for parentheses/brackets. The argument is also similar to the one I made below. I would either use:

man_pages = [('index', 'pythondevelopersguide',
              u"Python Developer's Guide Documentation",
              [u'Brett Cannon'], 1)]

This takes 1/3 of vertical space compared to the "expanded" version (but I would only use it in case of a single tuple) or

man_pages = [
    ('index', 'pythondevelopersguide',
     u"Python Developer's Guide Documentation",
     [u'Brett Cannon'], 1),
]

This takes roughly half of the vertical space, and I would use it if I want/need more horizontal space or have (or planning to add) more tuples.

It also depends on the context: if it's a module-level constant I can splurge a bit and waste more vertical space, if it's a variable or a function call in the middle of a 10-lines function, I would avoid making the function twice as long if possible. The fact that the style is context-dependent is also the reason why I generally avoid using tools that alter the formatting I used.