I feel that the default position of the group and form RSS buttons is slightly too far to the right and they should be spaced about 4 pixels to the right.
If you disagree, then I assume it wouldn’t be hard for me to modify a copy of the default theme to appease my sense of aesthetics? 
The other thing that doesn’t look quite right to me is how the text and icons are not vertically centred in the buttons.
Are these things concious design decisions or open to discussion about being changed?
I can only speak personally but I don’t think it is really so much about ‘design decisions’ or ‘discussions’ as it is about ensuring that the end user can change things to their own preference. The simple fact that we may be happy with the way something looks and is laid out is fine with me as long as we give users the opportunity to customise. and hopefully we have managed to do that. Where we may have inadvertently failed to do that then when we hear about it we try and correct it wherever possible. Which is why supplied themes and stylesheets are not yet necessarily nailed down.