Calling yourself a rationalist means, basically, that you're a virtue-ethicist who considers rationality to be a virtue: you're willing to allow for the maximization of truth at the expense of (some amount of) utility. In its way, this is a signaling mechanism like any other: there's no "rational sense" in doing something that will earn you locally sub-optimal utility, even if that thing is rationality itself.

However, like the local signal of revenge allows for global cooperation in the iterated prisoner's dilemma, maximizing for local truth is a clear signal to others that they can globally rely on your work to benefit all parties equally (including them), rather than just whoever the rationalist works for. Succinctly, "no one has their ICBMs pointed at the enemy's universities."