Misleading error message when trying to add comment into a locked issue

This happened to me at https://gitlab.gnome.org/Community/Engagement/General/issues/39 and it's related to issue #43697 (moved) too. While I've been writing my comment some other user locked the issue for new comments, but I didn't know it. When I wanted to submit the comment a red bad opened with an error message:

Your comment could not be submitted! Please check your network connection and try again.

There was nothing wrong with my connection, really. I (accidentally) noticed there had been added new comments after my attempt to add my comment, one of them showing the issue had been locked.

When I open the issue URL at the top now, there is no comment entry any more.