For HN I would think almost all the complexity is in rendering. That’s a job for your browser.
What’s left is things like the max length for a title (not too problematic to count that in code points or bytes, I think)
The big risk, I think, is in users (mis)using rendering direction, multiple levels of accents, zero-width characters and weird code points to mess up the resulting page. Some Unicode symbols and emojis typically look a lot larger and heavier than ‘normal’ characters, switching writing direction may change visual indentation of a comment, etc.
Worse, Unicode rendering being hard, text rendering bugs that crash browsers or even entire devices are discovered every now and then. If somebody entered one in a HN message, that could crash millions of devices.
What’s left is things like the max length for a title (not too problematic to count that in code points or bytes, I think)
The big risk, I think, is in users (mis)using rendering direction, multiple levels of accents, zero-width characters and weird code points to mess up the resulting page. Some Unicode symbols and emojis typically look a lot larger and heavier than ‘normal’ characters, switching writing direction may change visual indentation of a comment, etc.
Worse, Unicode rendering being hard, text rendering bugs that crash browsers or even entire devices are discovered every now and then. If somebody entered one in a HN message, that could crash millions of devices.