Invest + Blood of the Preserver XP (L5R rules board)

A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.

A player, 14 September 2014

If I buy back a dead personality from my discard pile using Blood XP, can I invest him?

Furthermore, the CR states "...a player may increase it's gold cost, once, ...". I assume the word "once" refers to a player being unable to pay more than the invest cost to get the benefit multiple times, but what is the duration on the "once" condition? If my dead personality referenced above was invested once before, can I invest him again? Assuming I'm allow to invest him at all, of course.