Welcome to the nuthouse. I had to make a similar post back in July (which you can see since it's f-locked). I notified the mods of the communities that I belong to in order to give them a heads up in case my troll decided to spam them too. You might want to consider that if you think your troll will try to get their jollies elsewhere once being blocked from your LJ.
You can also use a stats tracker to see how often this IP reads your journal even if they don't post. I did that and discovered that my troll read me daily - sometimes multiple times in a day - which just seems bizarre. Why read the LJ of someone you dislike? Oh, wait... troll=no real life. I forgot. ;-)
. troll=no real life. I forgot.
Exactly. It amazes me that some people have nothing better to do.
Where do you find the LJ stats tracker?
You can use the code generated at statcounter.com If you put it in your user info page where HTML is allowed, it works fine (you can't track individual entries). I just needed an idea of how often a certain IP hit my various sites. It works in more detail on my own website. LJ limits what info is returned, but it was enough to let me see how obsessive the freaky neighbor is. :P
Though it is no longer active, using Component I had a free stat counter on -all- of my LJ pages for a good year or two.