With the present Subscription workflow if the users doesn't then visit the thread, either via the link in the Subscription email message, or directly, any follow-up messages posted to the same thread do not generate thread update emails to that subscribed user.

Is there a way this workflow can be disabled, and users always be sent messages for any new thread posts?

This is a common request from our forum users.

Steve

Would you like it to disable for just a certain thread, or for all threads?

It's actually more technical question than users preference. Users may specify an email address which stops being working or checked, then your server will just send a lot waste (and perhaps will get back a lot of undelivered messages). Also if some topic gets a reply, then an email notification is sent, and later, more replies are posted, there is no sense to sent a notification about each of them. The link sent in the notification, gets a user to the last unread message and s/he could follow the thread to read further. In a case if a lot similar emails are sent per each post, there's a risk to get your server blacklisted in spam databases.