When editing a quote, be sure to leave the quote markers ([quote][/quote]) at both ends of quote. The first one opens the box and the second one closes it. Without both, the ‘greybox’ will not form.
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There are several options for adding more than one quote to a post. The easiest for me would be to simply have a second YBF forum window open and copy the quotes from window 2 as I bring them up using the quote button to the edit box on window one. I know that sounded complicated but in reality it's not.