I'm a woman, and my boarding pass with United has 3 letters added: SRA (meaning Mrs in Spanish). Let's say my name and passport name is "Laura Andrea Smith", well, according to United my boarding passes read:

"SMITH/LAURASRA" or LAURA SRA SMITH

(SRA LAURA SMITH according to their website, meaning Mrs. Laura Smith). I tried to change it, I would like to have this SRA deleted, also I'm single, so not Mrs. Smith me. I emailed United with this specific request and never got an answer, nor the SRA deleted as of today.

Aside from that, I haven't had any problems with my boarding passes, at least not in the US and Canada. I think it is because all your info and full name is actually on their computers and linked to your partial name printed on the boarding pass. Hope it helps.