Unique subdomain for user

It is not in Cobalt because you cannot make it purely based on Cobalt. You have to configure your server.

But it is possible to do.

You can create domain alias that *.domain.com is an alias to www.domain.com. That is it. You can enter sergey.domain.com and www.domain.com will be opened.

Then you can create small plugin that will parse domain, find user by subdomain and set appropriate URL parameters.

What i want to say it is not hard to do if you know what you are doing. But it is imposible to do with Cobalt because it cannot control server settings or configuration.

Then you can create small plugin that will parse domain, find user by subdomain and set appropriate URL parameters.

Interesting! Would like to see a tutorial or usecase article in the knowledgebase area ;-)

Would like to see a tutorial or usecase article in the knowledgebase area

This is not related to Cobalt at all. This is general knowledge of server technologies and HTTP protocol. In fact you can do that to any extension. And requires a lot of hacks.

For example you need subdomain name. You cannot use user name because it can contain non-Latin characters. So you need to add interface too change user subdomain with all required validation. Also you need to hak core router and change URL to subdomain if there is USER_ID in the URL when you create SEF links. And some other things. But not even a word about Cobalt :)

It is possible in terms that URL part may contain any characters. But it also should be one one profile level. And this might be done very easy just by creating your own router.php