I'm interested in this topic, because I hear so many saying they're only allowed underground, etc.
By WI code (we do our own thing, but it's not lax standards, imo), we can use flexible couplings anywhere so long as it's "installed in accordance with the manufacturer's instructions," and Fernco allows "in home" installations on vertical pipes in their documentation. They say the pipes need to be supported, but then we fall back to our own codes regarding that.
I haven't dug into other code to see if they say otherwise, but I'd be curious if there is a limitation specifically stated.