Can I trust in visual inspection to identify LED terminals?
Super-Red (AlGaAs) LED dice are mounted the opposite way of most others, so they appear backwards from the silhouette of the leadframe. 

The leadframe pin length should tell you the difference but there's been a case of one identified in another question here that's reversed even for that (presumably so they didn't have to buy two leadframe types or trim them differently- it's described in the datasheet so it's not an error). 

So, the bottom line is "no" you can't trust anything that's not specified in the datasheet (and even then, stuff happens, I've seen a 1N400x diode with reversed markings, presumably dropped and replaced on the line- post test, pre-marking by a worker in Taipei where the factory was at the time).