The option for uninstalling apps "--unmerge" is not an opposite of "emerge" but rather an opposite of "merge". I suggest changing it to "--submerge" or "--drown" but leaving the old one too for compatibility.
As I tried explaining to you already, this doesn't really warrant a bug report as the meaning is correct https://en.wiktionary.org/wiki/unmerge As a side note thought please look into using --deselect and --depclean as a safer way to remove packages in Gentoo.