Revert Notification has multiple flaws that should be addressed.

Revert's justification should be clearly given to the target user
When a revert is performed with an edit summary added, the revert notification presents some unneeded information.

If you give a reason in the edit summary, you get the full edit summary, which includes the default revert message with the revision, something not necessarily needed:

If the edit summary gets longer, in particular, because the "Undo revision by" gets longer, the reason will be truncated for sure:

We should drop the "Undo revision by", as this information is unimportant and already said below. The edit ID is a piece of information for established users, which can be found in the edit itself. What matters is the page (already given in the primary message) and the reason why the revert was performed.

Not giving a reason should display an invite to contact the performer
If no reason is given for it, it could look unfair, and it is likely that newcomers won't try to edit anymore:

In lieu, we should have a default message that would invite to contact the user who performed the undo:

$1 didn't gave a reason, please contact them.

It is a good way to make users who are easy undoers to take their responsibilities and document.

Is the icon conveying a bad message?
The revert notification is quite violent and I'm not sure that the icon helps. Maybe we should use an information icon instead.