@Johannes_B I've scheduled it here to match the planned physical event in Rio: we have arranged a workshop there
@Johannes_B The plan in Rio is to talk about what needs to be done to better support accessibility, for example does the LaTeX kernel need 'tagging hooks'
@Johannes_B I hope it will be useful to invite contributions from here too
@Maïeul well calc hasn't changed since 1990 or so. It changes the behavour to allow arithemetic so you can't argue that it should not change behaviour. It would be just about impossible to implement the syntax \global\setlength even if you wanted to implement that.