Can't seem to find an easy way to find these? I did a search in StudioU for my username, but finds nothing. You can see a list of comments under your profile but thats not a very logical place to look.
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You can find this post helpful as well.
The easiest way I can see in a quick look is to click on your name at the upper right and look at your profile-it shows you all activity you have ever done, but I did not see a way to only see which topics you started.
That said, I hear you that it's not the most elegant way to see all the posts you've started, and I've shared your feedback with the team.