Unable to type commas in hash-sign comments if there is other text on the same line

[etu]

This is a bit of an odd one, I haven't had the time to debug, but I guess it happens in: https://github.com/ssm/vcl-mode/blob/master/vcl-mode.el#L372-L384

When trying to type the regular comma character , in # comments that contain text emacs yells End position is smaller than start position in my minibuffer.

Examples:

vcl 4.0;

sub vcl_recv {
    // I use this sort of comments to describe the issue with the # comments

    // I can place my cursor after the # on the next line and type either text or
    // commas, it doesn't matter if it's a space between the # or not. So that
    // works as expected and would look like this:
    # ,

    // However, if I already have some text in the comment, I can't type the
    // comma character so it would look like this:
    # Test,

    // I can't put in the commas between two words either:
    # Test, test
}

Emacs Version:

GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo version 1.16.0)