When compiling for C# 11, this warning may appear:

warning CS8981: The type name 'keyvalue' only contains lower-cased ascii characters. Such names may become reserved for the language.

here: public partial class keyvalue : global::ProtoBuf.IExtensible

It's not necessarily wrong, but protobuf-gen already has an Escape method for all known language identifiers, so this doesn't seem like that big of a problem, perhaps this warning should be suppressed?

Mildly related: protocolbuffers/protobuf#9981