The Merge glitch happens every once in a while. I see it about once every hundred races or so...it's pretty rare. It always makes me laugh tho. I'm glad it doesn't happen more often, it would begin to bug me if cars merged all the time.
Not to sound like a snob, but using the AI as a wall is generally frowned upon by hardcore racers. We all know it can be done, it's no big surprise to most of us here, and most of us choose not to bounce off other cars. Why? Because it's a cheap win. It's much more rewarding to use your racing skills, squeaking by the other sim cars with delicate timing rather than smacking them about. Plus, it's simply realistic. If you used another car as a wall in real life, for sure your @$$ would be black flagged off the track...you'd possibly be banned for the rest of the season!
Now I'm not saying that occasional touching doesn't happen between cars; sometimes it's impossible to avoid. The AI will show a total lack of common sense like 75% of the time and will think nothing of pushing YOU off course. I mean, you can play your game however you like--I really don't care. All I'm saying is that the best human drivers race better than the sim cars. They show a bit of racing finesse. Make sense?