As far as I understood the spec for the TEXMAP extension, the check would only require checking for lines starting with "0 !: 1 ... FILENAME" and handle them as "1 ... FILENAME". I've implemented this, now the checks result in "file ok" for the catamaran (thanks for pointing to that example!). 
The alternative would have been to search all comment/meta lines and therein count sub-part-filenames as "used". This would be extension-safe for all other extensions using file references, but it would (a) slow down the check and (b) also accidentally count files as used even if they are only used in real comments (for example after changing a reference and keeping the old one for history/user-information purpose as in this example). I've implemented this and removed it quickly as (b) came into mind...
So my question is: are there any other known extensions using file references, LDInspector should take care of?
The LDCad-specials should be taken care of already (thanks again for your help Roland!).
The alternative would have been to search all comment/meta lines and therein count sub-part-filenames as "used". This would be extension-safe for all other extensions using file references, but it would (a) slow down the check and (b) also accidentally count files as used even if they are only used in real comments (for example after changing a reference and keeping the old one for history/user-information purpose as in this example). I've implemented this and removed it quickly as (b) came into mind...
So my question is: are there any other known extensions using file references, LDInspector should take care of?
The LDCad-specials should be taken care of already (thanks again for your help Roland!).