How will I ever be sure that I will get the value of my burned BlackCoins back??
No guarantees.
I read on poloniex "BLK will be delisted on August 2. You will have until that date to trade relevant pairs on Poloniex, and up to and including September 2 to withdraw your BLK."
Does that affect when the burn will start or end at all?
Unlike snapshot, burning does not depend on exchanges.
The best option is to take out a portion of BLACKNET for free distribution to BLACKCOIN holders.
Maybe 30%，They supported the blackcoin，Please give them some comfort，Don't be a cold person.
Then take a part to burn, maybe 40%. Long-lasting burning，Just like EOS is a long time ICO.
The rest are used to develop, promote, market, Reward people.
.
It is best to burn for a long time.If the burning is completed once, it is unfair.
Maybe you don't agree with me,
but，If you want blacknet to succeed,You must learn from others' successful experiences.