Here's something that I heard and that Imms only would know and be able to take advantage of:

Do your level gains and other improvement issues benefit from immediately choosing a sphere at level one? Meaning if you don't choose your sphere until level 9 or something, your hp/mana/mv gains from 1-8 will be less than what they would otherwise have been?

Indeed, as a general question, are there little things like that that nobody really could know of unless they were familiar with the code, and hence be staff-only information? This is the sort of thing I think people talk about, or surmise.