Hey, I've heard there's a limit to how much you can RS and you can't buy from shops anymore if you buy too many things. Is that true?

This mostly comes up because I hoard Ratskeller Inn items. After a good RS can I clear the shop out? If not, what's a good way to get all the things?

Also, when sometimes all the shops around Subeta are empty/nearly empty--why?

There is a limit or so I've heard - I'm not sure though but I think it's pretty high as I've never hit it personally. The shops are empty sometimes because they periodically clear out all the stocked items and switch them with fresh ones. If you catch that just right is how you get the rarer items since you've got to beat everyone else to them. I don't think the Ratskeller items vend so RSing them probably is your best bet for hording. And if you on the freyalise trading company angrybeard might give you an item if you help him.

i'm pretty sure RS bans only happen when you restock a bunch of R45+ items in a short period of time. i'm not completely sure though, someone might correct me :P

Not sure about the rules on exactly when you get a ban, but one of the first things I did when starting on gourmand achievements was go into every food shop and buy one of everything in stock so I'm sure you'll be fine. Most Main Shops tend to have more items in stock than the Rathskeller Inn anyway.

And the shops clear periodically, there's not a set time when they do anymore (other than, when I'm ready to start restocking they usually do -.-) but that's why they're empty.