This annotation correctly generates a multiline comment when used with Jankson, as you can see here:

The ingame tooltip however does not reflect this correctly:

Possible solutions to this problem would be to either add your own @Comment annotation using Components that gets transformed to the Jankson one when serialising (with the component being transformed using getString), or to respect "\n" and/or "\r\n" when transforming @Comment annotations into tooltips and add new lines accordingly