Limit by section in Weighted Search
I've also seen this issue myself when using weightedsearch and as a result I have jsut gone and created a solution for this by adding a new parameter to the substringSearch function.

I've also commented on the issue which was raised back in January on the weightedsearch github page and added my updated files as a zip file, so please feel free to download it and give it a go if you wish. By putting it onto the issue tracker they will hopefully pull this feature into the plugin in a future release now.

You can see further details here: https://github.com/wja-no/craft-weighted-search/issues/1