This is one of those ideas that is so simple and elegant that it makes you think “why did I never think of doing this?!”
Neat trick! I don’t think I’ll namespace everything this way, because there’s some aliases and commands I run so often that the comma would get annoying, but for other less frequently used helper scripts then this will be perfect!
I do something similar with build trees, naming them +build, +cross-arm etc.
This convention was suggested by the GNU Arch version control system years ago (maybe 20??), but it's really useful for the same tab completion reason and I have kept it for almost two decades, even when I switched to git.
It was suggested by Tom Lord (RIP), who used it heavily long before he wrote GNU Arch.
File names or directories starting with a comma where considered “junk”, and ones with a plus sign I think where considered “precious”.
Maybe then try ending your commands with a comma so that you don’t break first-char autocomplete !
But that's the killer feature for me! I always forget the little commands I've written over the years, whereas a leading comma will easily let me list them.