This has been fixed for the Photo and Image components as well as the File component. The functionality goes something like this:
Extensions are derived from the text following the last dot instead of the first
Except the special case of files that end with .whatever.gz
Names/Titles of files are derived from the remaining part of the filename
File component Titles now use the same code as the Image and Photo components to make them ‘human readable’ (dashes are changed to spaces, and Words Are Capitalised.
Original report
See the following example. The problem is that the code for deciding on the mime type in templates/component/file/en.html seems to assume that extension starts with the first dot and not the last one.
Also since MKDoc assumes that the title of the file is just up to the first dot it means that the title cannot be properly edited — the title should be upto the last dot.