> Could these lead to conflicting names?

Nope.  See the behavior in the spec for when a custom matcher with the same name is defined multiple times:

https://github.com/rspec/rspec-expectations/pull/332/files#diff-abfe7962870ca97bd12c8f86a47253f3R66

> What happens if the class name is all non-ascii?

See https://github.com/rspec/rspec-expectations/pull/332/files#diff-abfe7962870ca97bd12c8f86a47253f3R76 -- not ideal, but the best we can do I think, and I'm not super concerned about this case.