If you paste an entry from an external application (such as a word processing program) into the Rich Text Editor, the Rich Text Editor will automatically insert HTML markup to preserve the formatting. To avoid this, you can switch to the HTML editor before you paste your text into the entry (this will remove all the tags and formatting that would have been inserted with the text), or switch to it afterward (this will show the tags and will let you remove the ones you don't want).
Rationale: this isn't specific to the problem boredinsomniac wants to address with her proposed addition to FAQ165, so I would make it a separate FAQ (or add it to an existing FAQ) and link to it from FAQ165 instead.
