One of the big annoyances in Evolution for me was when setting the composer preferences the options for "automatically insert emoticon images" "start typing at the bottom when replying" and "keep signature above the original message when replying" were grayed out and unusable.
The biggest for me was the "keep signature above the original message when replying" because even when using no signature when replying you would need to manually hit return a couple of times to start a fresh reply just above the original message.
The quick fix can be done in gconf-editor by going to the apps section in the left sidebar, when it's clicked you will evolution, it's in alphabetical order so it's easy to find, click evolution, then mail, now composer. It should look like this.
If yours was like mine was before this fix you will not have the boolean keys for "magic_smileys" "reply_start_bottom" or "top_signature"
To add these right click in a blank area of the editor and click new key and type in one of the above keys without the parenthesis and choose true or false, this will check or uncheck the option in Evolution.
If you want all the options create three individual keys. Close gconf-editor then open Evolution, go to Composer Preferences and you should have all the options available.
This will also automatically add space above the original text when replying when you have the "keep signature above the original message when replying" checked in composer preferences.
I hope someone finds this useful. I know it has made Evolution a lot better for me.