So, I think I may have found a bug in the current version of Dokuwiki, where a blank line is only considered blank if it doesn't contain any spaces.  Let's try it out!

The previous paragraph is separated from this with a true blank line (no spaces no nothing).
 
This paragraph is separated from the previous with a line containing one space.
  
This paragraph is separated from the previous with a line containing two spaces.

There should be 4 distinct even though short paragraphs above this one.  I suspect you only see two :-)