This is why I stick to standard ASCII.

Mixing R-L and L-R scripts (as has been discussed here on many occasions) is a ripe arena for mysterious behavior. Given that even monolingual texts in R-L scripts will often include L-R characters, it can get hairy quickly. A desire to try to avoid having visible markers in text around the transitions is partly why the Unicode spec around bidi text is so complicated.

Disappointed that xn--sei.com or <insert fleuron here>.com is apparently registered but not redirecting to ornately decorated texts.

If you are using plain text and don't have access to HTML or CSS markup, you can follow the RTL character with U+200E LEFT-TO-RIGHT MARK to achieve the same effect. And even if you do have access to those things, using U+200E ensures that operations that strip markup (like copy-paste) don't break your text.