For example see this thread:
But I believe it may happen on all threads across YT. I haven't done the research.
The minority that uses Modern aren't being heard on Classic when replying to threads started on Classic.
Rustyfarmall and sflem849 are prolific contributors who only use Modern. Lately they cannot be found on Classic.
Can't you just kill one format or the other. The dual presentations have never been completely compatible. I don't care which one gets trashed but I suppose others will.