This is a very wellwritten post and it makes some very good points. Thank you for bringing my attention to this!
First off I have a question since I'm not yet familiar with every aspect of this platform: There is a difference of about 7% between total supply and circulation supply in steem according to the numbers in your article. What is this "non-circulating supply" and why is it accounted for separately from the circulating supply?

Inflation is exactly what you have stated: The increase of the supply of money and nothing more, nothing less (despite that every government on earth are trying to con you with badly manipulated CPI:s etc.)
That being said, this doesn't have to mean that SBD is decreasing in value, compared to USD or any other national currency, since there is a demand factor to it as well. I couldn't find any recent numbers on user growth only a 2 year old article stating 3% user growth in 24 hours (probably has slowed down since) and more users obviously mean more demand. There is also the potential for rising demand outside of the platform among consumers and speculators, so in theory the price of SBD could go to infinity even at this current inflation rate.
NOTE: I'm not saying it will or should go to infinity or even rise at all, just that it could in theory.
Obviously demand can also decrease among both users and outside the platform and that would naturally have the opposite effect.
In short: inflation rate is only one of several factors that determines the exchange rate to USD albeit a very imortant one and certainly someting I will keep in mind.

Again, thank you for a great post!