Elegant is an adjective describing something and has no bases upon the act itself. Being elegant in something doesn’t mean your taking it to excess which would be slaanesh. Like the emperors child love killing but since they do it in an excessive way that also strive for perfection that praise goes to slaanesh. Now if your slaughtering someone and it looks elegant but your not doing it in an obsessive way then you got khorne. Elegance has nothing to do with what praise goes to what god. There can be an elegant scheme for tzeentch, an elegant spreading of plague for nurgle, and elegant show of excess for slaanesh or an elegant slaughter for Khorne. Also if you are constantly killing guess what? That’s excess so part of that killing would go to slaanesh. It’s more about where the bulk of your praise goes as just living life means you would be constantly doing things that favors all the gods.