Aside from not running off on your own, attitude is a big part of being promoted. If you're lippy or clever with people, especially a corporal+, you're not going to be high on their list of people to recommend for promotion. Not to mention, it's not like you're the only person who's ever gone long periods of time without promotion. My first 3 years of SSTRP I never made it past the rank of PFC. Why? Because of chance. Because somebody was in the right place at the right time and I wasn't. Not to mention other people were just simply better than me. There's no shame in it.
Yes, I was the one who played the separatist. The mansion was almost cleared of separatists with the last of them holding out on the rear porch. I decided to make my final stand on the roof, when I see Strauss trotting around on top as I come over the rise. I have no clue how you made it up there, but I stood behind you for nearly have a minute with a machete before I finally just whacked poor Strauss off. I didn't even intend to PK 'em, that's just how it turned out.