How does such low quality submissions comes to main page when so many of good quality submissions struggle to show up? I'm not implying any fraud or anything but genuinely wants to understand how "SEO" on HN works.
Gitlab's Handbook [0] (which this article is part of) is an invaluable resource for any first time founders. This is one of the best contribution of Gitlab to the community in my opinion.
We have been using typescript in large scale JS project with 15-20 library modules and 7-8 product modules. I cannot think of building such product without typescript. When we compile all libraries and products and see no TS errors, we know at least that we are referring to correct properties, and wiring the shape correctly.
Typescript has bunch of "clever" things but you don't have to use it. We probably use 30-40% of TS features and that is more than sufficient for us. With that said, here is what I think about your questions.
1. Agree, and it is not any better without TS either. In case, a library is not compiling with your TS version, we ignore the error, put a FIXME there and remove the "ignore" sometime later
2. Yes but that is not TS problem. Without TS it is even worse.
3. Agree sometimes, we get so complicated errors. We search around and see if any smart people have figured what that means. If not, ignore and move on with a FIXME
4. Since many years, we are not writing any JS which doesn't need transpiling. If not TS, you would be using babbel or some other tool most of the time anyways so we haven't this to be an issue.