Total control?
Does the person who made this submission have the right to delete it even though by doing so they delete your data?
Do other users have the right to delete your data?
Total control for you means denying someone else the right to delete this conversation.
Do other users have the right to redefine your data by changing the context surrounding it?
If you posted "I vote for this too" to some very sound proposal to allow changing of usernames, and then the original author changed the proposal to "Bestiality should be legal", thus suggesting to the world you support such a thing... did the other user have right through the control of their data to substantial modify the context of your data? To the point that the other person could create a personal liability for you?
Where do the lines start and end, if your content can stand alone then the issues are not there. Almost everything in a forum is a discussion, conversation, argument, debate, an interaction depending on the context of other people's content. The minutes of those things are a record of fact, that someone said something and someone else replied and said something else. Content on a forum is never detached from the content of others.
I agree you have the right to your data, but disagree someone has the right to modify those minutes, those records of fact, to impact the data of other people in any way.
A forum is a collective work, and the rules for a collective work are different to the rules of a personal work.