Inaccurate vim emulation in marker placement when using insert-mode remappings

Describe the bug

Making a remap that creates a marker whenever exiting insert mode leads to incorrect marker placement.

To Reproduce

I like to make a marker whenever I exit insert mode. Here's a toy example where I replace a word via this approach:

Starting with this file:

this_is_a_variable = old_name
new_name

Using the vim command sequence:

gg$ciw<esc>mfjyiw`fp

Yields the following modification to said file:

this_is_a_variable = new_name
new_name

This behavior is consistent between vim and VSCode.

In vim, you can automate making the marker f with an insert-mode remapping:

" when exiting insert mode, the marker f is made
inoremap <esc> <esc>mf

And equivalently, you can create an equivalent mapping in VSCode with the following settings.json file:

{
    "vim.insertModeKeyBindings": [
        {"before": ["<esc>"], "after": ["<esc>", "m", "f"]},
    ]
}

This shortens the command sequence:

before: gg$ciw<esc>mfjyiw`fp
after:  gg$ciw<esc>jyiw`fp

Unfortunately, this remapping only works in vim, revealing a bug in VSCode's vim emulation of marker placement.

Expected Behavior

Applying the new command sequence, instead of this:

this_is_a_variable = new_name
new_name

you get this:

this_is_a_varianew_nameble = 
new_name

The marker is displaced left of it's correct location, and by an amount equal to the difference in line length before versus after the change (c) operation. In general, it appears that the difference in characters before and after insert mode determines how displaced the marker will be.

It would be nice if this were fixed, or if a hack existed to correct the behavior.

Environment (please complete the following information):

• Extension (VsCodeVim) version: 1.25.2
• VS Code Version: Code 1.81.1 (Universal) (6c3e3dba23e8fadc360aed75ce363ba185c49794, 2023-08-09T22:20:33.924Z)
• OS Version: Darwin arm64 22.5.0

Reproduce the issue using the insert-mode remapping in settings.json and the shortened command sequence described above. Trace how marker placement is updated after the change operation, and consider the work complete when the marker remains at the same logical location and the example produces the expected file contents.