Depends on
how you look at it.
Technically, I guess leveling past 100 was a waste of time, but on the other hand, did you have something better
to do? I'm sitting here at level 154, with hyperinflated stats (both from playing and from a bug back in
early alpha), but I'll still be flushing it all down
to dive into the retcon game. While there's no magic button
to return yourself
to your previous level, there's nothing stopping you from leveling all over again.
(although, you could invent something not only copied from KoL - which I stopped playing cause of huge complexity and boredom)
While things in TH are certainly inspired by KoL, I tend
to view retcon (and ascension) as nothing more than the webgame version of "New Game+", so I don't view retcon as KoL's ascension lifted clean. We've also set things up differently, and I like
how we've worked out retcon; I think it'll give players more flexibility than they have in KoL.
Will I be able to transmogrify during retcon[?]
If I recall things correctly, you will still be able
to transmog during retcon, in the middle of the run if you so choose. The only requirement is that,
to initiate another retcon, you have
to hit at least level 11. The upshot of this is, if you accidentally retcon into the wrong class, you can fix that easily.