This is the title of a discussion about self-reference The perplexity about self-reference among philosophers has always stuck me as hilarious. As if language ought to be up to the artificial standards of philosophers, rather than philosophers themselves dealing with artificialities. It's like that joke about the guy who only ever looks under the lamplight to find his keys, and then complains that because they aren't there, his keys must have winked out of existence. Self-reference is everywhere and perfectly ordinary. If philosophers would like to make them into anomalies, that says more about the failings of the philosophical imagination than language.
As for the relevance of self-reference: it draws attention to the event of language, it's taking place. It's the institution, at the level of the proposition, of the what is extra-propositional in language. When language takes itself as an object, the separation of language 'here' and object 'there' evaporates: language becomes enthinged, enworlded. Or rather, the always-already enworldedness of language shows itself and stops being obscured, for the briefest of moments. Self-reference is puzzling only to those who want to treat language as a pure, self-enclosed system, sterilized from any imbrication in the world.