This isn't an exact answer to your question, but I had a similar experience recently with American Airlines.
My surname is long, being in 2 parts separated by a hyphen, and their system somehow managed to mangle everything, resulting in something not unlike what you have on your e-ticket; if anything a bit worse.
Never at any point was there a problem. Again I realise that it wasn't United and I am not you, but personally I doubt you're going to experience any difficulties. The correspondence is clear between what's on your e-ticket and your passport.