At this year's vigil to close the School of the Americas I helped to coordinate a fantastic team of professional interpreters who donated their services. There were also several groups who preferred to have their own staff organizers interpret for folks, so I again had the chance to listen to activists interpret consecutive into English who have been thrown into interpreting with no training. I totally get that groups want to control the message, and feel like their staff will have better rapport with the speaker, but I was reminded of two serious mistakes that untrained interpreters commonly make.
The first mistake comes off to me as a lack of respect for the speaker's voice. These activists added things to what the speaker had said. Perhaps because they knew the details and thought it would make a more compelling story, or in one case the interpreter tried to express that he was speaking in his own voice as he added a campaign ask, but he didn't know third person rule. Now really, it's not usually appropriate for the interpreter to add anything, even in this way, but if he HAD to, he could have said "the interpreter would like to add that ... (eg. this information is available in English at the website x)". If the interpreter needs to ask for a repetition this should also be requested in third person (eg, the interpreter requests a repetition).
This leads me to the second common mistake I saw, which is slipping into third person for NOT that reason. Most activists thrown into interpreting seem to know you're not supposed to say "he said, she said" - but still strangely fall back into it from time to time - particularly in the Q & A. The reason this is like nails on the chalkboard to me is that it weakens the speaker's voice dramatically.
Please, if you ever hear folks making these mistakes in social justice settings, take a minute to remind them that the best way to respect the speaker and amplify their voice is to not add to, omit from, or otherwise change the message of the speaker, and to use the first person unless they are referring to themselves, in which case to use "the interpreter".
(photo is of me interpreting on stage at the vigil for Martin Almada - thanks to my mom for making us fantastic red interpreter vests that made us easy to identify!)