Experience with double last names and flying SU?
 

I am a regular Flying blue flyer, and I am trying to test different airlines and of course get miles. Decided to give Aeroflot a try. Have booked a r/t trip from Europe to Asia. Since I could not book directly with Aeroflot, due to my long name, I booked on another website, once payment went through my confirmation shows my name the way is supposed to be, i.e. "Name" "Lastname" "Lastname2".
However when I checked on Aeroflot's website my booking it shows instead: "Name" "LastnameLastname"
I phoned the airline in my country, and I was told "don't worry, it's because in Aeroflot you cannot have spaces on the last name field. It will be fine"

Anybody else having similar experience, should I be worried that a different employee might interpret the naming situation different?

You won't have am issue due to this on aeroflot..
Note that many airlines handle lastnames that way.
To ensure your miles get credited, keep a photo of your boarding pass.