I have several areas of my website set up not to be indexed by search. I have done this in the asset tree weights page in the search manager.
What I do is select the asset at the top of the area I don't want indexed, select 'all asset types', set unable indexing to 'no', then reindex that area starting from the asset at the top.
But any asset that is live and has public permissions is coming up in my site's public search.
I'm pretty sure this was working before we upgraded to 3.18.11.
Am I doing something wrong? How can I stop those pages coming up in my site search? 
About to lodge an SLA support ticket if no-one has anything to add…
Hi Rachel
I might get a chance to test this one for you as I think we are both in the same boat at the moment.
I can add more on another front…
I just found that if you are safe editing a page and change content as well as the container type (wysiwyg to raw HTML) and then cancel the safe edit the contents of the page get overwritten with what was in safe edit.
After talking to Squiz this is apparently a 'known issue' with 3.18.11. Deleting 'sub' a couple of times in search_manager.inc fixed it.
Being the non-technical person that I am (I did not do the above!) I can't give any more detail than that but if you are having this issue then I strongly recommend talking to Squiz cause it is an easy fix! 