I stumbled upon this issue because I think this is a potential improvement. One of the reasons I don't use it is due to the outdated UI but since it also generates HTML doc for installed packages in a virtual environment I find this to be a useful feature like rdoc (ruby), rustdoc (rust) and are actively maintained helping documentation of third party packages too for local reference.

I have less knowledge about CSS but I tried updating css_v3.diff with master and added boostrap.css from CDN to pydoc which adds spacing along with improving layout and font. Attached is a screenshot that is looks better with the CSS patch and bootstrap. Including bootstrap is not lightweight option in the Python distribution but can be seen as a proof of improvement.