RESTEasy includes its own parser of service loader files (in the RegisterBuiltin class). That parser doesn't account for comments, even though those are legal (see https://docs.oracle.com/javase/9/docs/api/java/util/ServiceLoader.html). That makes for some interesting error messages when using e.g. RESTEasy's support for MicroProfile Context Propagation, because that file does use comments: https://github.com/resteasy/resteasy-microprofile/blob/main/context-propagation/src/main/resources/META-INF/services/jakarta.ws.rs.ext.Providers