Briefly describe (1-2 sentences) the Bug you’re experiencing:
-When you merge tasks, one is closed (naturally) in favour of the other, but all the comments and subtasks content is lost. Expectation (and requirement) is that all content is merged into remaining task/subtask.
Steps to reproduce:
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Welcome to the Asana Community @anon97625738 
This is not really a bug that is how the merge feature works.
You might consider moving one task to become a subtask of the other one to have all the info available. Otherwise a link is always added so you can quickly access the other one.
I have also found this feedback request thread for you to upvote: Merge Duplicate tasks - including custom fields and comments
Perhaps I should be clear - this would then be a “feature request” - I doubt that most people expect to lose the information in one entity when you merge it with another - you expect to have them “merge” like a zipper, as it does in other software systems. Can you please add it to the feature request list?
The workaround really doesn’t work that well, as now you have duplicate tasks within each other…