Sputter/Rough engine at start?
 

So my BRZ is less than 2000kms old. Today it was cold wet and raining. When I started my car, it "coughed" a few times once the engine started. The whole car shaked. I hope it wasn't a knock or anything. Is this common with this engine? I haven't been able to reproduce it yet. Car drives normally afterwards.

My 2015 FRS will do that on occasion. When starting after having sat all night it may misfire once or twice during the first 10 seconds or so.

With only 2200 miles on it I can not comment on what long term harm might be associated with this behavior.

No idea, but my '13 has done it on cold starts (below ~50* F) since I bought it last year.

At 12.5:1 compression it's surprising that the car will start at all when cold (the wonders of modern technology!). I'd say a misfire or two on start-up is relatively normal if it's only when it's cold and there are no other noises associated with it.

I used to own a 2ltr Renaultsport with 11:1 compression that would misfire when cold consistently. I owned that car for 5 years, did at least 40 track days in it and drove it hard everywhere (once warmed up) and it never once used a drop of oil and ran strong until I sold it.