While reviewing some code I looked at vscode's "problems" view and noticed, that the messages the lit-plugin extension adds do not have an indicator where they come from. In this screenshot you can see, how other plugins add such information:

(Notice the decorators "eslint(...)", "ts-styled-plugin(...)", and "ts(...)".)

In this particular case it would have helped me to quicker identify, which vscode plugin my coworker is missing.