Usually the least amount of words conveyed the better. Being concise & to-the-point is important in communication. Don't get me wrong, details are what the Compendium was made on, but long blocks of text can be intimidating. That being said, I'm not against either as long as the post is entertaining or interesting. If you post a large block of text (which isn't necessarily a "long post" thing as much as it can be a "i don't understand forum layouts and how to split paragraphs well" thing) I think most people recognize the probability that it will be glanced through or possibly even skipped...now, if you make that large block of text boring to the extent that it's no more than an eye-burning letter-spew not even the FancluboftheTriforceofEternity would read, then we've got problems. lol
