Thanks again for the useful information L.K! After reading all this, I go for the lazy solution ;-)
For the present, I've added in Wishlist.cshtml:Link too long? Use goo.gl to create a short version
(Attention, the shortened link is case sensitive)
The next stadium will be an own link shortener on an own domain, as I prefer not to mix the code for shortening in Nopcommerce. Moreover, I can choose a shorter domain name and program it in a way it use only lower case characters.
In fact, similar as Amazon does with amzn.to ;-)
Many thanks for the input!