Fwiw, I submitted very similar concerns to this form. Discussion on Reddit, including with Foundation members, has been pretty sympathetic to the position of mrustc and other projects in a similar position. This is a comment form, let's hope they take the comments into account...

First, this is not Mozilla, but the Rust Foundation, a nonprofit funded by industry. Second, C does not have any trademark holder because it is defined by an ISO standard, making it nearly impossible for anyone to maliciously register a C trademark. Similarly C++. Many other languages, like Swift, *do* have registered trademarks. It's fine if you think the concept of trademark is silly - I agree. But given that we live in a society with codified trademarks, it's pretty important not to let some other company maliciously trademark the term. Since trademark law requires actively defending held trademarks at the cost of losing them, it makes sense to define which situations are appropriate for the Foundation to trigger defense of the trademark.