Thanks for your contributions to the site over the time you've been here. Like some of the others I'm a bit surprised by the extremity of your reaction after reading through the chat logs. I can definitely see how you may have taken Washu's response the wrong way, and perhaps it wasn't ideal for a moderator to make that type of joke -- but I can also see that he was simply responding in jest and did in fact continue on to begin explaining how the forum software displays which topics are closed -- albeit after you had bid the chat fairwell, and perhaps after you had already closed the window without your departure being registered.
We've also been told that our moderators are sometimes too serious and should be more easy going, so we're stuck between a rock and a hard place trying to please everyone with a consistent moderation style and instead leave decisions up to individual moderators depending on the situation, and I don't think Washu could have predicted that his small joke would result in you immediately leaving both the chat and the site itself before he could continue to be more helpful.
I also see another misunderstanding in the chat log -- before Washu's joke -- that doesn't seem to have been addressed yet. You asked (paraphrasing) "why it's productive to leave locked topics accessible", and Washu's response was "because it gives you a recent objective example of what not to do." Your response to that ("Huh? Like 'reading the new content on GameDev.net?' Is that what I 'should not do?'", "I don't see anything saying 'You should not ask people to make your game...' int he thread instructing people.", "I just see 'Okay dude, you're an involved community member and you just read ALL this stuff, and now you can't give your advice.'") seems to indicate that you took this as being directed at you, but I believe it was actually the answer to your question: the productive point of leaving a topic that can not be posted in accessible is that it provides an example for other beginners who may be considering a suitable post.
Briefly returning to one of your points from above, you said that "I don't see anything saying 'You should not ask people to make your game...' int he thread instructing people", but the second response from sunandshadow to the topic indicated exactly that: "We don't allow anything that could be described as recruitment or hiring in the regular forums. So look near the top of this page for a button that says Classifieds." The same sentiment was reiterated in the sixth and final reply from Tom Sloper.
You said that this was your first complaint/suggestion, and Washu was obviously the first moderator you contacted with your issue; although I can see from the log that Washu was continuing on from his joke with some more serious conversation, if you weren't happy with his response there are many other moderators you could also talk to, and as you can see from the responses to this topic there are plenty of people who are willing to listen.
This is a community and if you would like to see changes you can be a part of making them happen -- as such, and given both the apparent misunderstanding and the number of people who are willing to politely listen and respond to your feedback I would encourage you to reconsider -- but if you really feel you should leave because of this it's obviously your decision.