why there's no "subscribe to the topic" as a usual link (but as a checkbox in post message frm)? that's why user can't subscribe without posting some messages, even he doesn't want. i think this function must be moved from 'pthread' to new one...

Read about the option $emptySubscribe.

Paul
Read about the option $emptySubscribe.
yes it is, but i said about that it's not comfortable "to post empty message" even it is for subscribing, why cannot you do it like function not like an option of 'pthread', with normal link?

If you turn on your imagination, you could do it yourself as an addon :-) In a case when $action is equal to 'vthread' or 'vtopic', provide a code for the variable, let's say, $emailNotificationsLink in bb_plugins.php and this code will be actually the JS function which submits the empty form.