Thanks, for that information. Since I have no coding knowlege I reached out to stackexchange for some help for a workaround. Question is here: https://emacs.stackexchange.com/questions/35626/how-to-make-my-own-org-mode-text-emphasis-work-again
One guy mentioned this after I wrote about this bug report:
"If they don't want items added to org-emphasis-alist they shouldn't use the repeat customization type which allows insertion and deletion. Furthermore, they should add a note about this restriction in the doc string of org-emphasis-alist. Maybe, you can give a follow-up in the bug-report about that."
So I did what he requested. He also provided me with a working solution. Even with that said I might ask if you could consider supporting adding new emphasis definitions in the future? For people like me who are not able to write a function to solve the problem in an instant this customize option is like the red carpet already lying on the floor.
With kind regards,