Systemd developers, if you're reading this: this isn't the sort of bug where people grumble for awhile and then get over it, because things are still broken, and the workaround being circulated (KillUserProcesses=no) doesn't fully work. (https://github.com/systemd/systemd/issues/8486) As long as people continue to encounter this issue anew--and they still are--people will be angry at the systemd maintainers.
The bug you've linked to was closed[1] by the reporter with "Thanks for the clarification guys. Much appreciated!", after it was pointed out to them that something they were trying ho do with "KillUserProcesses=no" was better done in another way.
1. Edit: Not literally closed by the reporter. Lennart Poettering closed it, "closed by the reporter" as in "the issue was resolved to the reporter's satisfaction".
