add some clearer points to IRV comparison

[wolftune]

• That the spoiler aspect of IRV happens in a range of support that is inherently between low-popularity of a candidate and high-enough-popularity to win.
  • I.e. Rather than being an edge case, the spoiler situation is almost inevitable for any candidate or party who grows in popularity over multiple elections or similar instead of jumping from low to high popularity (technically, this assumes that a party's growth isn't drawn 100% from one other party)
• That the IRV issue can be easily described as "splitting the vote" in rounds prior to the final one
• That any rank system with less rankings than candidates leads toward lesser-evil voting and vote inequality
• That the history of IRV in practice indicates dominance of 2-parties rather than enabling 3rd- and 4th-party inclusion

[nardo]

Please review the current text on the site -- lot of rework went in that takes into account these points, but want to make sure the essence is captured.