I love those beanbag-chair, not corp environments. Not everything that isn't corporate is 'unprofessional'. Wearing trainers to work was unprofessional, until it became established; now tech CEOs compete on who has the most expensive sneakers.
> If HR was involved, it's because someone was out of line or just doesn't understand how adults manage boundaries, in which case he should be warned and, if the case merits, punished.
I assume you mean the person who said it? It's also possible the person who reported it doesn't know how to manage relationships, or had some other motive in reporting this to HR - you can speculate either way.
Directness, professionalism and - yes! - impersonal conversation - is what I would generally prefer.
And as for competitive dressing. Bring back uniforms is all I can say to that.
Edit: grammar
The hardship begins when personal and professional relationships mix, but if a personal relationship is established it's reasonable to assume that both people should know how to deal with eachother and would have cleared this up between themselves. If HR was involved, it's because someone was out of line or just doesn't understand how adults manage boundaries, in which case he should be warned and, if the case merits, punished.