Russian Imperial Stouts

I brew a IRS several times a year.
Grain bill s
Maris otter
Black patent
Roasted barley
Dark chocolate
L 60 or L80
Munich @10
Flaked barley
And sometimes
Smoked malt
Cara Munich
Special B
Busket malt.

Never used lactose.

 

Because lactose is unfermentable by your typical sacch yeast, it'll add body, sweetness and a heavier mouthfeel. If you were to brew a stout that you thought was too dry or thin, you could always add it when bottling/kegging. Also maltodextrin is another alternative, and I don't think you'll get as much sweetness as you would with lactose, but I could be wrong.

But to answer your question yea it's used in imperial stouts. Southern tier has a few examples – 2X Stout and their Creme Brulee

 

Lactose shouldn't really be used in an RIS, but that's not to say some people aren't using it…but to me, it wouldn't be an RIS if lactose was used, it would shift over to an American Imperial Stout.
It should always be stated imho cause there are a lot of lactose intolerant folks out there. Lactose is fairly popular in American imperial stouts and obviously milk stouts, but not required. I've used lactose several times through the years in stouts, mainly milk stouts, most recently on the new "mexican stout" styled brew, but I always warn people before they drink it.

 

I don't use lactose in a RIS, but it is possible the homebrewer did.