You can't use the Analyze Point tool on read-only files presumably because it is trying to add annotation but sometimes people just want to check measurements such as slope between geometry in a read-only files and this is a very useful tool to do that.
I wouldn't recommend opening files to check them; it increases risk of accidently editing the file. I agree we could make the tool work better in read-only files. Until then, I would recommend making a personal working file and referencing in the data you need. This is especially important if that data is interdisciplinary.
That's a good workaround but someone who is dipping into design models for checking or enquiry shouldn't need to setup a new file to do so. Fairly minor but just not ideal and was thinking it could be an easy fix if it's possible to use the tool in read only files?
A workaround is to reference it into a personal working file.