http://nasomi.com/wiki/index.php?title=Config:AshitaQuote:
- Q. Which plugins/addons are authorized?
- A. distance, tparty, timestamp, and recast. These are already loaded by default when launching the game, except for recast. To load recast, type /addon load recast.
There are reasons why, yes. The simplest is that they aren't in era.
As for dat replacements, generally they are tolerated as long as they are only cosmetic changes (eg. XIView). Anything that gives you a gameplay advantage though is not allowed.