Original as in the English version?
Afaik especially American English uses capitals a lot. So to them it is optimal
Copying conventions from one language to another does not seem useful to me at all, they are language-specific by definition :p
Changing Dutch would not be a problem I think, if all translators agree. Changing the original strings is a different matter though, I don't know what the project policy is about that. I believe the strings from the original data files are used. If that is really the case, they cannot be changed, as it would mean changing the original files.
(Which can be done of course, but then you cannot distribute them.)