When I insert NBSP in the paragraph and render it with RtfDocumentRenderer, I get additional space after NBSP, and it is slightly noticeable in the resulting document.
Document d = new Document();
Section s = d.AddSection();
Paragraph content = s.AddParagraph("Before NBSP");
//this results in the following RTF code: Before NBSP\~ after NBSP
//while correct code is: Before NBSP\~after NBSP
This bug was spotted in version 1.32.4334.0.