Sorry, what exactly is this "top block thing", on which StackExchange site?
I didn't manually block anything from these sites, but don't see any annoying block near the top.
Well, the main "stackexchange.com" has a dialog-box-like element titled "StackExchange Q&A Communities are Different. Here's how:", with a bunch of content, and a [Learn More] button. You can close this with the X in the top right corner. Is this it?
I guess it doesn't bother me because I've never found that site useful to begin with.
The dismissible block is not actually at the top; it's below the "search all sites" toolbar, and below that block there isn't any particularly useful content, just "hot questions" and a sidebar of "featured sites". Basically nothing other than that toolbar is useful, and that toolbar could just be a tiny browser extension or something. So if I dismiss that box, no useful content moves up to occupy that space. It could bother me a bit if I were interested in browsing the hot questions, rather than search.
Maybe DuckDuckGo has a shortcut for it? Hey, yes it does: !se
If you use DDG, you have no need to visit stackexchange.com just to search all the SE sites; just !se in front of your search terms.