Is it safe to consume packed tea leaves after their expiry? After all they might have lost their flavor, but can they be harmful in any way?
Yes, generally, especially if you've kept them in good conditions. (If the package has been open and it's damp and they might've grown a little mold, that's obviously bad.) The expiration date is for purposes of quality, as you've noted; it doesn't indicate anything about safety. So give them a quick inspection, see if there's enough flavor left for them to be worth using, and go for it.