This guy in the YT vid below is reviewing LED headlights for his Accord but in the background, listen to the tapping and clacking of the engine in the first 3 minutes; best heard at the 45 sec mark. I hear this exact noise in so many 6th gen 4-cyl engines. Doesn't seem to harm anything, though. My engine has sounded like this for the past 30,000 miles or so despite me being the original owner and maintaining it well. Had the valves adjusted by the dealer a while back without any change. I later isolated the noise to the driver's side of the engine. Perhaps an accessory or something under the timing cover...?

 

Honda engines can just get noisy, especially with VTEC's moving parts and all that. From what I understand there are parts down by the valves that can wear out and create noise. Going between M1 5-30, M1 0-40, and Rotella 5-40 didn't quiet my engine down at all. But it's not much noisier than a stock FRS so I'm not worried.

 

I have the same car, just the valves/rockers (valve lash). You can adjust them but usually when the engine is cold and the parts are cold (with a bit of free play in the rockers) this is what you hear. More of an issue with high KM too. No harm done.