As I recall, itext uses completely different structures for pdf tables and non-pdf tables, making it very difficult to write a generic "table" component. Since the RTF and HTML generation was more of a toy idea, I didn't spend any time on it.
If you feel like doing some coding, I'll be happy to point you in the right direction and make sure the code gets in. Otherwise, I'd suggest opening a JIRA issue and getting others to vote on it. If there's enough interest, we could add RTF support to the roadmap.
Thank you very much for the fast anwser :-)
Right now I am using indentation on <p:paragraph> to solve my problem. But thanks for offering your support. I will drop you a note when I feel like doing some coding concerning tables for RTF! :-)