Articles that are created as "searchable" appear in search results (which is good). Articles that are created as "unsearchable" do not appear in search results (which is good). However, if you create an article that is "searchable", and then later edit it to be "unsearchable", it still appears in search results. Reindexing does not affect the behavior.
Steps to reproduce:
1) Add a Basic Web Content article. Leave the checkbox as "searchable". Publish it.
2) Edit the article. Uncheck the "Searchable" checkbox. Publish it.
3) Add a Search portlet to a page. Search for the article.
That the article would not appear in the search results.
The article appears in the search results.
Reproduced on Portal Master b2999a1421716a369c6cb706c6966ef332419999
The behavior for 6.1.30 EE GA3 is a little different. When you edit the "searchable" article to be "unsearchable" in step 2, it does remove the article from the search results in step 3. However, after a reindex, the article reappears in the search results.