My apologies for not taking the time to check you out. I normally would, but not at 3 am on a smartphone. I am in the southern hemisphere (until next Thursday).
To my mind, there is no such thing as informal writing. I am not sure of your age, or perhaps you are American, but no such thing exists. In the days when we wrote letters to each other, we wrote as much in a formal English, as we would if we were writing for publication.
My late father (degrees in law, engineering, journalism, and fluent in 11 languages) wrote to me once a week while I was at boarding school, so I am, I think, aware of how personal letters are written.
In those years, I also received many personal letters from many other people. Nobody wrote in anything other than a formal manner. Writing is formal. Speaking, depending on tbe situation (or language) is less so.
With regard to the use of ellipsis, it is used when tbe writer has already mentioned something, and the writer is quite clear that tbe reader knows what is being referred to. It is not used as a means for the writer to appear mysterious or as an indication of passing time. In publication circles, it is always avoided. I have worked for newspapers, magazines, and book publishers. It doesn’t add anything to the pie and is best avoided. My late father also reported for Reuters during the war years. You can also check out his book ‘Memoirs of a Jewish Journalist in Nazi Germany.’
When I read something, no matter where it is, I expect to read it in correctly written language, and amongst those of my generation, that is the general expectation.
My daughter’s generation was taught that one doesn’t need to use correct grammar so long as one is understood. What a load of ignorant bollocks.