The author takes it for granted that accessibility issues are more prevalent in proprietary software like Discord (vs FOSS alternatives), is there any evidence to back this up? I ask because it seems counter-intuitive. Since most proprietary software in this space tend to have more users than their FOSS counterparts, it seems pretty straightforward to think that accessibility will be less of an issue in the former category (i.e., more users = taking into account and addressing more accessibility needs vs when you only have a few thousand users).
Maybe the logic is being open source encourages volunteers to address accessibility issues and submit patches? Although even that's debatable; unless the project is quite popular, there will always be shortage of volunteers.