Sure, but your identity persists across all subreddits. If someone makes an insightful comment on a programming subreddit, for instance, and has a high karma score, you may be disappointed to discover that 90% of their previous submissions consists of cat pictures, jokes, in-depth cartography discussion, and porn.
I guess reddit just feels 'diluted' to me. It facilitates a broad range of discussion and does so fairly well, but I can't think of a subreddit that is actually the best place to discuss any particular topic. It's generally my second or third stop.