In the past, we submitted this kind of issues as bug reports (e.g., BUG #16625) describing how PostgreSQL may manifest suboptimal runtime performance for certain query patterns, which suggests missing optimizations. However, the developer who responded to our reports suggested reporting these issues as missing optimisations on the Wiki page instead.
Furthermore, we also noticed that users could be unaware of these issues and inquire about possible workarounds, which would be a further reason to provide this information on the Wiki. The Wiki would also provide a forum for developers and users to discuss opportunities for improving the existing query optimizer.
I am looking forward to your response and would be happy to provide any additional information that you may need.