Actually, when I started this site, I was worried we'd get so many visitors, I'd have to pay for more bandwidth....so, I'm a little suprised too. My explenation is that this is really more of a site of interest to creators than it is to casual comic fans...and creators are busy people. It's part of the reason I'm not on here more...
partial copyright characters are very easy to use, as long as you use the original character, and not the new version you are more familiar with. "Partial copyright" is really a misnomer used to identify characters that have a more popular version that actually is copyrighted. Shield can be used, no problem...just use the original version from the PD comics. Disputed characters are harder to use because that means someone has a financial interest in keeping their use of a character exclusive...which means they might send you a scary cease and desist, even though they do not have exclusive rights. For example, Captain Marvel is now PD, but DC still markets merchandise, and there have been talks of a movie....so they might try to get you to back away....