Yeah I have read about it on here.Also I might be mistaken,but were not there a few self service check in kiosks at the HEX platform just 2-3 years ago...I might be ofcourse confusing them with HEX ticket vending machines.

Talking about airports that used to offer the service but have since discountinued the facility:

Moscow:All 3 Moscow airports used to offer in town check in at the Aeroexpress stations (trains to DME,VKO and SVO have always departed from diffirent railway stations),one could check in baggage and get the BP,but apparently very few people ended up using the service.

At some point S7 Airlines launched their own "in town check in" facility at Domodedovskaya metro station (you would have to get a bus from there to DME),but apparently it did not work either and they shut that office.

BKK: I remember there was a facility at Makassan station,but it's no longer working IIRC.


PS:Mods,maybe a wiki would be useful? I have included all the replies in the OP.