A few things to wrap this up and get something useful out of it.
Removing the closing buttons of tabs is not going to happen. This is just too of a widely accepted UI convention. On the same note, adding a special and obscure setting that will only ever be used by a handful of people is not going to happen, it's just not good design.
Adding an option to remove a UI element is basically admitting that it doesn't work, in this case though, it does work and you absolutely need a button to close a tab.
Having said that I take two things out of this thread:
1) Adding a little bit of a buffer distance so the close button is not right next to the tab name sounds like a reasonable improvement feature.
2) Sorting tabs in multiple rows needs some work.
— If you think any of those things will improve C3, you can file a couple of issues in our bug tracker and they will be looked at.