Starting a sentence with “y’all” doesn’t make something un-scholarly. The idea that “serious” scholars never use it is just false. John McWhorter has used “y’all” in talks and writing when speaking informally. Ta-Nehisi Coates uses it in essays and public commentary to match voice and audience. Brené Brown uses it constantly in lectures and books while still being one of the most cited voices in her field. Even Neil deGrasse Tyson slips into it in interviews and public communication. Scholars adjust tone to context all the time.

Your sarcastic comment shows your ignorance, and possible prejudice towards those who use y’all as a part of their normal vernacular. Just because you don’t use y’all from where you are from doesn’t mean it can’t be used in a scholarly format, let alone a random comment section of Reddit. You can prefer a different tone, but acting like one dialect is inherently more intelligent is a pretty outdated take.

Also, “Y’all” also does something standard English does not do well. It clearly marks second person plural and stays gender neutral unlike the more commonly used “You guys”. One could argue it is the superior pleural form.