I don't see how that makes Element responsible for matrix.org content. Thunderbird offers getting an email address via gandi.net in their new account page. Does that mean that Mozilla is suddenly responsible for all emails (like spam) coming out of gandi?
However, the non-profit Foundation (https://matrix.org/foundation) was set up in 2018 with myself and Amandine deliberately in a minority control position (2 of 5 directors, called Guardians) specifically to address this concern - to protect Matrix from Element’s commercial activity, in case we ever went rogue.
As it happens, The Foundation farms out hosting and admin of the matrix.org homeserver to Element (which makes sense, given the Foundation doesn’t have employees and Element was already running the server), but if Element ever went evil, i am very confident that the Foundation Guardians would kick in and make a course correction.