When I interpret and at the end of a long meeting the participants end up saying something like, "Oh, yes, Mr. Violet, I almost forgot you were here," of course that's a high compliment. They were able to concentrate on their discussion. One of my main goals has been achieved: they connected almost as if they spoke the same language.
Nevertheless, I have now heard the term "invisible" used several times as if it were some kind of ideal. Let me juxtapose this:
"I remember working at meetings when the delegates remained silent after the speeches but always broke into applause after the [interpretations]." (Norman Langford, ILO, 1948, Birth of a Profession, p. 27)
OK, this is rare and only for consecutive of long speeches where the interpreter's performance is highly noticeable and quite welcome.
And there's no doubt that when the interpreter is noticed it should never even slightly, if possible, hinder or influence the course of events.
Nevertheless, in a multilingual event there is something happening, linguistically and more broadly. Two or more cultures are finding a way to accommodate each other. Even when two corporations or NGOs meet, in their manner, maybe their dress and in their speech, those identities are reflected. They may even issue badges to distinguish one group from another. The presence and visibility of interpreters are more likely than not part of a set of signals that naturally characterize a multilingual event. I don't see "invisible" as a goal. But maybe that's just me.
Read more on this by Jan Rausch on Monika Kokoszycka's wonderful blog using the button.