I own an SEO and Internet Marketing company... I completely understand your fears, however I'm here to tell you that when you do searches for any of the domains I've ever posted in the wordpress forums, the forums are the last thing to show up.
One little link in a forum is not going to jump to the top of the search engine results for you... I promise.
However reading back, I see that you solved the .htaccess issue - and you're looking to figure out how to change the word "category" to the word "versioni" - I'm personally not sure how to do that, although I think you should start a new thread for this new problem... people are seeing your title to this thread and thinking you need help with .htaccess files, not with changing the names of permalink defaults.