Are there any guides to advanced search on the EA Forum. On my mobile, when I do a search there are no advanced search options. And if I search for communism for instance all the results are for community instead. If I put communism in quotation marks that doesn't change a thing.
site:forum.effectivealtruism.org communism should work, as a google search
We actually deployed a whole new search backend last week, and it looks like you found the first bug.
I've created a pull request on Github that should fix the quotation marks not working, and you can expect that to be live on the site in 1-2 days. In the mean time, your best bet is probably the Google search with site: that Neel mentioned.
Thanks for letting us know!