However, it's not quite like a chat in the pub because there are no accents nor colloquialisms in the written word. It is either correct or not.
If there are no colloquialisms in the written word, someone must have forgotten to tell my daughters (and many/most of their generation!) - although you might describe them as 'just incorrect'!
In the context of this thread, one irony is that in a pub (or any verbal communication) there would be no discernible difference between "their" and "they're" (or "there")! However, the point about the pub analogy is that both are very informal/'casual' forms of communication/interaction - and, although one is verbal and the other is written, a good few people write (casually/informally) what they would say in verbal communication. It's also the case that people vary their 'style' according to the situation. Returning the my daughters, both have serious professional roles (one is a barrister) and one assumes that they write professionally is as grammatical correct as they can manage. However, what they write in 'informal e-mails' (not to mention text messages and 'social media'!) doesn't bear looking at for an old fogie like myself!
... and nor is it necessarily a question of ignorance. I rather doubt that I'm the only person whose typing fingers sometimes go into a "phonetic autopilot" mode, and type the wrong one of there/their/they're (or "its"/"it's" etc.), even though I know which should be used, am I?
... your use of 'what' (instead of that or which) it reminds me of Ernie Wise.
"Like" (which
does sometimes get into written material) is far worse one amongst the younger generations! Also, as from 'ignorance', most of us are far from omniscient when it comes to grammar - had you talking about using "that" instead of "which", or vice versa, I would be the first to admit that I haven't a clue as to which is 'correct' in which situation!
Whatever, as I implied, I hope that we are not going to see too much of these discussions in the future. If there is a lack of clarity, then we should ask for clarification, but if it is clear what is meant, I'm happy.
Kind Regards, John