And is this the main reason as mentioned there:
"If you have Bitcoin on loan at the time of the fork, you do not have it on balance and therefore you cannot receive corresponding Bitcoin Unlimited."
Because in case the new coin might get more advantageous, you might loose the chance of owning it from the very beginning?
But in the end there is no risk of losing any coins, but only the value to them, right? To my understanding... but if where you stay will be kind of random after the fork has happened, isn't it just luck how your coins will split? What if they totally transform to the new coin and it has half the value of core?
oh this is just getting more complicated to a newbie like me (although I've read that other long post published recently in the forum), I think I'll just copy your actions
When you have bitcoin on loan, you only receive one coin.
Let's say bitcoin will split in BitcoinOld and BitcoinNew. Poloniex only gives you one of them.
When you have it on your own wallet, you will have coins in both chains, so when you have 1 bitcoin now, you will have 1 BitcoinOld and 1 BitcoinNew.
The value of those coins are uncertain. Especially shortly after the fork price will drop. Then after a while there are in fact three options:
1) the BitcoinOld chain survives, because the new coin has not enough power.
2) the BitcoinNew chain suvives, because almost everybody will follow this
3) both chains survive.
In fact, there were forks in the past, but never with substantial consequences. Just a minor part dropping off of bitcoin, fastly correcting themselves to be on bitcoin again. If 1) or 2) will be the case, I guess there is not much harm done.
But if both chains are big enough to survive, then there will be a uncertain situation, with price dropping. In fact, we have one example of this: the hardfork in ETH. The new ETH chain needed quite some time to reach a price level as before the fork (and is now much higher), but the ETC chain needed more time. If you hold both coins at that time, you have a nice portfolio now, but only after a year of uncertainty.
EDIT:
I called them BitcoinOld and BitcoinNew, because there are several forks possible the next months. I will hold them after things are more certain, because you have BIP148,BIP141,Segwit2X,BU,Bitmain-coin etc. all with different dates so even after 1 August I will wait some time.