So... we could consider easy communication with aliens as akin to fantasy. OTOH, it also ranks as being an accepted part of the convention, no matter how unlikely.
Maybe our SF rules need a subcategory of conventions that, strictly speaking, do not fit the accepted rules of SF, but have been accepted nonetheless:
- Star Drives
- Time Travel
- Psi Powers
- Communicable Humanoid Aliens
Anything else for this list?