We're the same.

Confluence's inline and bottom-of-the-page comments are excellent. You can have proper chained discussions.

Blog posts have been amazing for us to share small "experiences" like how somebody setup their environment (as opposed to more standard env setup documentation). These tend to be more informal.

Markdown files in repositories have been alright, definitely good for readmes. However, they suffer because our tooling (Gitlab) does not support comments on the files.