I am not saying that selfvoting is wrong, but there are many users who clearly just develop strategies to post empty content and self upvote all day long - for no community or social purpose.. Doing nothing to improve the attraction of the community to new users, for example.

this means to create content and on average selfvote a min. of 7 times just to break even.

Can you explain how you came to that conclusion? What is the average calculated on? A consideration of an average across the entire blockchain or average post payout?

If the value of Steem is $1USD and the inflation rate is around 8% per year - then holding $1000 of Steem Power (e.g. 1000 Steem tokens) would result in those tokens being reduced in value by $80 over the year - right? So you have to make $80 over the year in rewards to cover that.
At current rates (Steem is $0.83 currently) - a 1000 Steem upvote at 100% power results in $0.06 payout (According to steemnow.com's calculator anyway).. so if we say you can make 10 of those votes per day, that's $0.60 payout per day from that 1000SP. You used 7 upvotes per day, so that's a total of $0.42 per day reward payout. So to cover that $80 loss due to interest would take 190 days of self upvoting at that rate - by my calculations.

You propose that "investor's aim to minimise the amount of rewards they take" are you on drugs or what?

To clarify, I was specifically referring to rewards pool claims. I can understand why you would think this makes no sense and I did not say 'don't take any rewards' - but the maths I showed here appear to make clear that even if a poster posts literally nothing of any use, they can break even in just over half a year at the rate of self upvoting you described. The idea is to post content that shows proof of brain and to then benefit from that by taking a larger cut of the rewards pool. Obviously Steem isn't magic money and the rewards pool payments have to come from somewhere - this is a given when using the system. If we don't improve the network and/or post great content (which in turn attracts new users and more traffic) then we aren't really doing anything to produce the financial benefits we want to receive. Or did investment ROI suddenly become guaranteed while I was making tea?

The distribution of the reward pool has nothing to do with the steem price and price discovery

I think you obviously hogged that bong.. I can point you to people all day long who won't use or hold Steem because of the distribution of the rewards pool - which in turn lowers the price of Steem.

SBD was designed as a Debt Instrument, I can imagine that its function would be to pay for the costs to run the blockchain

To my understanding, SBD's purpose is to provide a stable peg to incentivise use of the platform. It's tough to go to buy a loaf of bread when the value of your currency has drastically changed since yesterday, hence the peg.

Why not take SBD off all external exchanges?

I have no problem with completely ending the use of SBDs.