Registered just to be able to request this feature.
If you have a task with a lot of comments (in real life we discuss a lot) having system messages mixed in with user messages makes the conversation hard to read.
At least group the user and system messages so a human can read other comments without scrolling and get distracted by not relevant messages.
System messages are very useful for investigation on who did what but add no value when you have actual comments.
Ability to delete your own system messages is absolutely against all system administrators rules.