First of all, thanks for your quick response.
[...] There is not always a good place to break a URL.
I do not know much about Textinfo etc., but I'll risk a naive question nevertheless. The documentation you linked states "TeX allows line breaking within URLs at only a few characters". Wouldn't it be better if the URL could be broken at an arbitrary position? That way, the length to cut could be made a function of some automatic fill factor, and wouldn't depend on where the URL happens to have some special break points. It may not be visually appealing to cut at a seemingly arbitrary position, but the alternative implementation often does not produce visually appealing results anyway.
[...] Increasing the ragged right space from 2 em to 3 em doesn't break any of the cases in that file, so I have made this change (commit 752656cc29, 2024-11-01).
I would imagine that a new version of the Texinfo tools will trickle down only after a few years. Is this space setting in \urefallowbreak something the user can tweak with the current version in most Linux distributions? Or is that a hard-coded value? Regards, rdiez