Why the 8 space indent? I think 2 or 4 are common (spaces, not tabs). Probably best to have formatting changes in a separate PR and doing it across the board, though in this case, I think the default of 2 spaces was fine.

It could be when Visual Studio does changes

looks like it was spaces but has been changed to tabs.

@wallymathieu VS will honor the .editorconfig settings. However, maybe this project does not have specific settings for fsproj files. In which case it will use whatever default your system has.

Here's a snippet for .editorconfig, maybe try that and re-edit & save in your editor, see what happens?

# Project files and app specific XML files
[*.{csproj,fsproj,shproj,projitems,props,targets,xaml}]
trim_trailing_whitespace = true
insert_final_newline     = true
indent_style             = space
indent_size              = 2
charset                  = utf-8

I agree. We should have that setting in editorconfig. Looks like we have not added it yet for this repository. Perhaps something you want to make a PR for?