Yes there is, Sebastian Phoenix can appear in a RE and steal sP from what you have on hand, so it's best not to carry too much at one time. It's a random percentage of what you are carrying at the time.
No, there is no limit :)
Maleria can also steal money from you - It's usually not much, a few k sP the RE says something like ' Maleria cackles and suddenly your sP feels a little lighter' xD
ooh, I don't know who Maleria is. I haven't gotten around reading the SubetaPedia yet. I'm gonna visit it tomorrow. :^)
I've been here for like 2.5 years and I don't really know who she is either, I've never read the subetapedia or anything but her quests are over in darkside and she usually gives pretty good sP rewards - sometimes cool items too, but mostly not http://subeta.net/quests.php/maleria
I think Phoenix's tax RE takes from five to ten percent of what you have in your pocket. There's Achievements for being taxed. I once went a year with nine digits in my pocket and didn't get taxed once. It's more frequent now though.
There's no limit to shop size. However big shops like mine have been giving the site laggity troubles and Keith (the site owner) does wish to institute a size limit. This has been threatened for a few years now and so far nothing has been implemented. Moving items out of your shop is a chore, so caveat vendor.
Way back in ancient history seven years ago-ish we used to have restock wars with Maleria the evil goddess on one side and Shinwa the good goddess on the other. Maleria also used to be a Battle Coloseum challenger and used to drop a highly coveted battle item . Her quest used ot ask for keyword items dark grey purple evil and matter, but now asks for weapons so maybe she's plotting something? She keeps on breaking Shinwa's bangle, how she gets a hold of it is??? We haven't really seen her out and about for a good while.
NPCs have changed their looks over the years, but she's always had the drag-queen dress.
Nowadays we've been more likely to hear from the evil goddess Merana because of the Islander Pirate plot (also a restock war) and Councilor's Cruise plot. She now announces new Hydrus curses around the time of her summer festival each year.
I think he takes from 1 to 10% actually.
Good news though, there are no more REs that steal items. Only the zapper can destroy items in your inventory as far as I know, and you can lock items to prevent this if you want to keep them in your inventory (: