Changing names causes confusion to ordinary users who tend to associate a certain continuous persona with a name.
There's so many suggestions to enable name changing that it makes one consider why it's so desired? Do you prefer to discard your identity every time you make a mistake or feel ashamed/discontent with what you've said?
Continuity of user names creates a more realistic, compelling sense of identity that influences the things you are going to say and how constructive or careful you're going to be about it.
Some people don't have this issue, but it seems that many trollish or irresponsible users would change names to try to evade consequences (thinking it would work) or manipulate attention for no good reason.
Name-changes aren't going to be allowed mainly because it adds paperwork for admins who have to set things manually and this forum's software isn't going to get any more upgrades ever again. Besides all that you most likely don't have a good enough reason to convince a half of the people who visited this thread that you're an exception, you can try your best, there's a separate contest for eloquence when results don't matter.
And if you really think your request should be considered seriously you should pm an admin about it.
