While I can't say I know anyone IC or OOC who RPs as coming from FFXI, there are two threads on opinions on the matter.
(super old, then necroed) http://ffxiv-roleplayers.com/showthread.php?tid=888
(very strong opinions. Locked thread.) http://ffxiv-roleplayers.com/showthread.php?tid=12533
Personally, I would suggest against it because while the worlds may be connected, they have a staggering amount of differences. While a lot of things do match up (I've heard units of time and measurement are similar/the same), calling a Roegadyn a tail-less Galka or the like is a fast way to get some crazy looks IC and more likely, a lot of ignoring OOC.
As said above though, if you've got a group of friends who accept that, go for it! The concerns are only coming from a "I want to RP with ALL open-world RPers" perspective, which means it's pretty clamped down. (Similar issues would arise if say, a group of people were RPing as real-life people trapped in the game a la .Hack, SAO, Log Horizon, etc. It'd be a completely different, but not bad or wrong, setting to RP in.) Most, if not all of the people encountered ICly have been born on Hydaelyn. (Because who knows if Primals are born and some other exceptions)
(super old, then necroed) http://ffxiv-roleplayers.com/showthread.php?tid=888
(very strong opinions. Locked thread.) http://ffxiv-roleplayers.com/showthread.php?tid=12533
Personally, I would suggest against it because while the worlds may be connected, they have a staggering amount of differences. While a lot of things do match up (I've heard units of time and measurement are similar/the same), calling a Roegadyn a tail-less Galka or the like is a fast way to get some crazy looks IC and more likely, a lot of ignoring OOC.
As said above though, if you've got a group of friends who accept that, go for it! The concerns are only coming from a "I want to RP with ALL open-world RPers" perspective, which means it's pretty clamped down. (Similar issues would arise if say, a group of people were RPing as real-life people trapped in the game a la .Hack, SAO, Log Horizon, etc. It'd be a completely different, but not bad or wrong, setting to RP in.) Most, if not all of the people encountered ICly have been born on Hydaelyn. (Because who knows if Primals are born and some other exceptions)