Line spacing in signatures tightened up.
I will take your grey font into consideration. I don't want to go black, but I'll think about a darker shade of grey ... it is #555555 right now which is pretty dark actually ... I think it might just look lighter because you're not used to it yet.
I don't plan on changing the ad box because it has worked out quite well this way, and in this position, for the past year, and it is our best performing ad size ... so I don't want to screw with it. Additionally, if everyone thought it was just "eww" then no one would click on it ... but it has a very high CTR, which is awesome for something farther down on the page ... so again, if it ain't broke, don't fix it.
I do understand your concern about the quick reply being further away from the blogs as a result of the similar threads feature. However, there are a few advantages to this as well. The first is that the similar threads feature, which is VERY handy, can now start to be used, as it was completely ignored farther down on the page. After all, once a thread has been viewed and replied to, who needs it? The goal is to interrupt that sequence and instead make it: (1) View question in thread (2) See if similar thread has more information I need (3) If not, then post reply ... Additionally, it will help to eliminate duplicate questions asked, because if someone's question wasn't answered in the thread, instead of replying, they might find the answer in a similar thread ... for that reason, I think it works good right above the Quick Reply box. The third reason is because right now, the Quick Reply box is right near the bottom of the page. With similar threads below it, it would be semi-middle/bottom of the page. Wondering why this is an advantage? With quick reply at the bottom, you can easily hit the End key on your keyboard to go right to the bottom where quick reply is. With quick reply somewhere in the middle of the page, you have to always scroll through a page to find it. Additionally, as always, you can hit the "Quick Reply" link in any postbit of the thread to instantly jump to the quick reply box.
Now ... the similar threads feature occupies about the size of one post. If you have to constantly scroll back up and down in a thread, I don't think something occupying the space of one post is the biggest hindrance ... unless it's ALWAYS the last post you need to refer back to, you have to scroll up through multiple threads anyways. If this is a concern for you, I suggest that you might find Threaded or Hybrid Thread Mode much more to your liking.