I have a hyphenated name and it doesn't seem to matter for boarding whether it's Mr Smithjones, or Mr Smith Jones.

Sometimes when claiming miles from other airlines they may query if the boarding pass says Smith Jones and my frequent flyer account is Smithjones.

I also get addressed by cabin crew as Mr Smithjo, which takes a while to get used to, as my full name is too long to print out for whatever system they use.