If you have:
Install A: node ID 100, "Dinosaurs"
Install B: node ID 100, "Iran"

And you submit a moreLikeThis query from Install A, passing the node ID of 100, there's no guarantee that Solr won't analyze the "Iran" article instead of the "Dinosaurs" article.

While the result query has an appropriate installation ID filter, the analysis query does not.

I've created a pull request for this:
https://github.com/ezsystems/ezfind/pull/13