I was wondering if the SQL Server 2017 (or SQL Azure) automatic index tuning feature would drop any unique index on a table, since that would be very bad for data consistency.
About the "Drop Index" option provided by Automatic Tuning in Azure SQL Database, unique indexes introduce a constraint that defines the table behavior, dropping them would change this behavior. As Automatic Tuning is designed to respects user defined constraints, unique indexes are not dropped.
Hope this helps.