Praiseworthiness is the quality of deserving praise — even when the thing was not a complete success. If a first try is clumsy but honest and brave, you can still talk about its praiseworthiness: it earned kind words, though it did not win. This is a long, rare, rather official noun. Most people never say it. They say “it deserves praise” or they use the easier adjective praiseworthy. You might see praiseworthiness in a careful essay or a report, where someone wants a noun for “the fact that this is worth praising.” It is not everyday talk, and it is not a word for showing off. Though actually, because it is so heavy, using it can sound a little stiff next to a simple “well done.”