You get the error message “Your query is malformed. Please rephrase your query.” when searching in SharePoint using the “None of these words” query. Spent hours trying to figure it out? I know I did..
This is actually an OOTB behaviour. The “None of these words” query can only be used in conjunction with another query, for example “All of these words“. This makes sense as the “None of these words” query is an explicit exclusion and can only be used against a result set, and not the entire content index.