Hi Manuel, and a warm (if delayed) welcome to WebmasterWorld :)
Thank you for posting a solution to a common problem, but as I'm sure you're aware, floated elements default to display:block which over-rides the explicitly set display:inline. This technique is usually needed for small amounts of text, not usually a whole <p>, so setting the para to float may impact on the layout of other elements inside .contentcontainer.
For me the real issue is if the WYSIWYG editors are incorrectly wrapping all text in <p> elements, rather then only using <p> for paragraphs ;)
But your reference to discussions about the SEO aspect of <p> is really interesting. Can you explain a bit more?