In case anyone is wondering why different glyphs have the same unicode code point, and how an app is supposed to decide which one to render... Well I don't know the reason for the first question actually, though many people appear to have some choice comments.

But as for the second question: for HTML documents, many tags have a lang attribute that decide which version of the glyph to render within that tag. Hacker News has lang="en", so it'll use a user setting to decide. For example, in Firefox' about:config, there's a setting called cjk_pref_fallback_order. If e.g. ja comes first, the little square inside the top square in 骨 is rendered on the right side, if any zh thing comes first, it's rendered on the left side.