There are a lot of issues 'solved' cleaning the user profile. And it is not clear what kind of solution it is, because it is not so easy for the users to recover the previous situation. A situation in the darkness for many users. And it is also not clear how we mark the resolution of a bug that needs to recreate the profile. The solution is more of a workaround than a real solution. This happens especially when upgrading the version of LibreOffice, and the problem usually occurs with the registrymodifications.xcu file. So at least having a comparator for this file, which would allow us to locate which option causes the problem, I think would help the developers very efficiently to fix the bug. And at the same time probably be able to provide the user with a solution without having to recreate the user profile.
We already have Edit > Track Changes > Compare document, which works on plain text files. Alternatively, there are command-line diff tools for users who know how to use them. But I can see the appeal of a one-click, customised tool that would make troubleshooting easier by reporting "these are the lines that are different to a stock .xcu file for this version of LO", and maybe an option to automatically remove personal information like what was filled into Tools > Options > LibreOffice > User Data. I think this would be blocked by bug 99716, as a lot of the diff would be related to base64 thumbnails stored in this file. Xisco and Buovjaga, what's your opinion?
Seems overkill to create and maintain as existing solutions are available.
But, the question for a user, find an easy way to what has changed, when they need to go for a clean profile. Facilitating to test what option is the source of the issue, and recover even manually their options. As you all know, there are a lot of problems with the profile, mainly when installing new versions of LibreOffice, generating a great frustration for the people. So it could help a lot to avoid issues, bug reports, and questions in Ask. Can be done?, but not so easy, it is a complex file. BTW Everything can be done,
I see Stéphane already added the instructions to do this: https://wiki.documentfoundation.org/UserProfile#Compare_files_to_identify_issues
For what it's worth, and at the risk of making the page unnecessarily busy, I added a section to the wiki, as Buovjaga noticed. I still feel a more sophisticated tool would be useful, as a diff is hard to navigate. But maybe something for an extension or downloadable script rather than something in core?
Better no to lose more time in this matter.