Proposed new version
Currently the template uses basic {{#switch:...}} which is a bit speghetti-like and is not very flexible.
I have created a new version using {{#var:...}}, {{padleft:...}} and {{#expr:...}}: User:Leduyquang753/NewOutdent.
It functions almost as the same as before, the only difference is when {{{1}}} is not a number, the outdent length will be the length of it instead.
The new version is fully backward-compatible.
Lê Duy Quang (Make some words | Contributions) at 10h21:20 | 2/10/2019 (UTC)
Add amount of outdent to the right of the outdent
As there can be multiple outdent times (and now reindent times), I suggest adding the amount of outdent to the right of the outdent by default, so that we can easily calculate the level of a comment:
┌───────────────────────┘ +9
Lê Duy Quang (Make some words | Contributions) at 13h19:24 | 2/10/2019 (UTC)