Automatically folding top-posted (or bottom-posted) blockquotes
One feature that I dearly miss from other mail clients like Geary, or web interfaces like GMail, is smart automatic "folding" of quoted stuff, in received (displayed) emails in particular, but also (to a lesser extent) in the mail composer.
The problem: 99% of the world uses top-posting (urgh) instead of the One True Way of "inline selective quoting", and we are left to suffer with it, terribly long messages that have a scrollbar for no good reason other than to make us scroll all the way to the bottom "just to check if there was something secretly inline-replied over there".
The idea, or at least that's how GMail and Geary deal with the problem that Outlook and GMail have created, is to fold the blockquotes and only unfold them when needed; i.e. when there's inline selective quoting going on. I suspect GMail also runs further analysis to determine if, in the case of a bottom-posting email received, the quote is complete (or if the person trimmed all the stuff before/after what they wanted to reply to, effectively doing selective inline quoting but replying only to a portion). GMail shows a clickable "(...)" bubble/symbol, Geary shows a "<=====v==v==v======>" bar with downwards pointing arrows. Clicking it expands the quote so that it can be read and replied to.
Again it's not as critical in the "composer" window than the mail reading window/pane, for me, because at least in the composer you can "ctrl+A & delete" as you start writing your reply (or you can even configure Evolution to not quote when replying); but for simply reading mail, you cannot escape the visual pollution caused by top-posters imposing their blockquotes onto your eyeballs, so I'd love for that to be automatically hidden.