I wouldn't worry about checking in with real people. I've flown 2 of these now (AA and UA) and both times checked in with agents at LHR. AA was no issues at all, nothing mentioned about LAN just a normal check in. It took the UA agent a minute to actually find the reservation as she was searching by ticket number or something but she found it eventually with again no mention of LAN. On my UA flight LHR-IAD-MIA and back I did miss my connection in IAD and went to the RCC to change flights. LAN was mentioned at this stage (I was asked what airline 045 ticket number was). I told her and she said she was just curious as she had never heard of that one before as LAN was an "offline carrier". No further problems though (apart from an unforced stay at IAD Hilton)

Have 2 more "LAN" trips coming up both LHR-LAX, 1 with UA and 1 with BA.