It seems kind of awkward to have them attached specifically to the OP's signature... I feel that the placement is intrusive, but even if it cannot be moved back to the bottom of the page, can it perhaps be separated from the signature a bit? Perhaps by placing it in its own table row with additional spacing?
I'll understand if they
must be placed mid-thread for some reason, i.e. advertiser demands or they're not getting enough clicks, but I think that they should at least be separate from the OP's signature. It seems like a simple change (given NAML's flexibility) and it'd be both an aesthetic improvement and a psychological one (putting ads inside the signature feels, at least to me, a lot like standing too close to someone and encroaching on their personal space IRL).
I don't mean to sound demanding or anything, and I do understand the need for ads (it is, after all, a free and high-quality forum; it needs to be paid for
somehow). It just seems odd to have them embedded inside the signature itself -- a space that, in my opinion anyway, users would tend to consider as being psychologically "theirs".