Would like to know more as well. I was not able to find further info on this.

Does anybody know more?

what i know is SBD is pegged to $1.

SBD is like tether or USDC. Its a store of value pegged to 1 USD. System always assumes SBD to be equal to one dollar no matter what the exchange rate is. This is the reason you can convert SBD for steem at pegged value even though its trading at .84$.

Now the reason behind it is simple. So you don't take money out of steem ecosystem. If you think that steem price is going to fall, you can sell your steem for SBD instead of dollar knowing that it will always hold its peg in the system.

Hope this helps.

Thank you for posting the question and an even bigger thank you for the steemians that posted the very informative answers!
I have learned a lot again today!

I'll try to explain this to the best of my ability. @tcpolymath gave me the best explanation asking to think of SBD as basically just "STEEM in a box". 

SBD is a smart contract  5% of debt was actually changed to 10% at HF 20. Until debt is at 9% you can choose to receive half of your payout in the form of SBD. At the moment of payout, the SBD received is equal to half the worth of you payout. This is where the "STEEM in a box" come into play.  When you convert your SBD to STEEM, it's like opening a loot box (or @steemmonsters booster pack) but without random elements. If you convert 5 SBD you get 5 USD worth STEEM. The existence of SBD has no effect on STEEM supply. 

Instead of suddenly stop printing SBD, between 9% - 10% the SBD print rate goes down in a linear way. At 9.5% debt you get your payouts 50% SP 25% SBD 25% STEEM. After debt level hits 10% the amount of USD (worth STEEM) you get per SBD starts to go down. 

SBD is basically a smart contract based financial instrument than an actual currency.

https://i.imgsafe.org/76/76e74ed503.png

The current 13,574,053 SBD supply can be converted to 31,554,338 STEEM which means you get 2.324 STEEM per SBD with STEEM priced at 43 cents. If STEEM fall a lot more in price, not giving 1 USD worth STEEM per SBD will keep everything afloat.

Disclaimer: I'm not a programmer or STEEM dev. It's best to consult an actual dev for the job.