@StylisticMoods then how about you unpublish such incomplete works, as well as promises of sequels on your complete works??
See, most of the times people don't really come to the message board first, so they might not read your pinned announcement first. They might see the number of stories you have written, and think "wow, this person has written so many stories, so we could assume she completes her stories"
And they would go through your stories one by one.. some are complete, some complete stories have announcement of sequels, and even such sequels have a few chapters in them, giving confidence that you have begun works on them so you would eventually complete them..
Only once they have gone through all your stories, might they come to your message board, to ask you when are you completing your stories, and they will see your announcement that all incomplete stories will forever stay incomplete!!!
You could save your readers a lot of disappointment by removing the incomplete works, which, as you said you aren't going to complete...
I don't think it would take much time to go through your stories and remove incomplete stories