Thanks for the kind reply :)
As for the investment argument, that's irrelevant since it doesn't change anything about how bad self-voting is. It's always bad, no matter how much someone invested, if any at all.
This debate isn't as much about what's currently possible within the protocol, it's more about working towards improving the incentive to vote on others, for example by increasing the curation rewards potential to far above a self-vote when voting on the right content. This would even increase the incentive to buy STEEM power in my opinion.