I agree with the OP on these issues, but I think it's also important to include that it is impossible to paint cichlid personalities with a broad brush.
Having worked for two maintenance companies and three fish stores, I can say that the #1 question people will ask about a cichlid is "will this work with my fish?" They are usually referring to other cichlids. I ALWAYS tell them that I can't make any guarantees with cichlids, but I can make suggestions based on experience from myself and others. The problem is that cichlids are "smart" as far as freshwater fish go. With that intelligence has come complex social behaviors and greater variability in personalities. You always hear people are saying "oscars are so mean" and then others saying "my oscars have always been pansies". This is more common with intelligent animals. You almost never hear someone complaining about aggression or other weird behaviors with the more-brainless fishes such as tetras and danios.
So cichlids are smart enough to have individual personalities, and when comparing one cichlid against another it's not only important to note the species (and it's lifestyle in the wild, as the OP mentioned), but also the personalities of the individuals you are trying to compare. Often this requires some guess-work, and we have all made the wrong decision here before. I don't see an issue with testing two fish together for compatibility as long as the owner is responsible enough to separate them if there are issues. But of course, the available information should be reviewed before blindly testing personalities.
