I haven't seen the rendered version but, based on the content, I think something like 30/70 might look better.
Also using the simple table markup (http://docutils.sourceforge.net/docs/user/rst/quickref.html#tables) might make the source shorter and more readable (same below).

Looks pretty good rendered.

Adjusting to @ezio-melotti's suggested width would shorten the first entry.

This is pretty much what I expected: it has too much whitespace on the first column and leaves less space for the description (e.g. the first description has to take two lines instead of one).
I think the simple table markup also figures out the column width automatically based on the content (and the list-table probably does the same if you omit the width, unless you want consistency between the tables).

Screenshot at 30/70

I think the simple table markup also figures out the column width automatically based on the content (and the list-table probably does the same if you omit the width, unless you want consistency between the tables).

No, it doesn't. The table is formatted this way because I configured the columns to be a 50/50 split, which I experimentally found to look the least awful. Unfortunately, while sphinx allows to set percentages for the table columns' widths it doesn't allow to do so for the table itself. Anyways, I'd like to keep the makup as is in this PR.

Fair enough.
Just out of curiosity, what did you find awful, and what were you trying to achieve (consistent column width between tables, full width table, others)?
(FWIW, of the two screenshots posted by Carol (thanks!), I prefer the 30/70.)

It is a separate exception that doesn't inherit from it?

Yes, sadly