P: Lightroom no longer accepts a dot in the catalog filename.

The reasons are not technical. Everyone is free to prefer his own code. But language (and characters) imply that you can be understood by others; there must be a minimum set of rules like spelling, punctuation, even common usage for SMS language.
Use of the dot character has been reserved for separating extensions since more than 30 years, the @ has a common meaning for anybody. Older users of computers and programmers have been taught to only use underscore or hyphens in file names or naming computer entities.
You are right that there is no technical reason in this case (since Rick Flohr admits it...), but the world is divided in two categories:
- those who are right to think there is no technical reasons; they will have problems some days...
- those who follow the good old rules; they'll never be bothered.

An extension is just a representation/interpretation of the given filename. Nothing more than making it easier for us humans to have an idea what a file contains, without having to look at the contents.

Sure, I could use some other separator. Point is there is no technical reason for the software to have this behaviour. Dots are a valid character in filenames.

Thanks for the reply. I'll await an update then :).

Dot in file name usually seperate the file name from extention (.lrcat), right?. Why not use _ or - in stead?