You have quoted wrong that is why your post looks a little bit weird.
Indeed, this is one of the biggest risks. DAO was an exception by now. There are only few projects which have needed a hard fork because of a really serious bug. That is why I always suggest to only hold a part of your money in crypto currencies. If you have made profit than exchange it. Well, if you have a problem with fiat money then exchange it to Gold or Silver or anything else. But going full into crypto currencies is always a risk.
"Not only altcoins, all cryptocurrencies should learn about this. It could happen to Bitcoin, too, in any way. It even happend already back in 2010 when a hard fork was conducted because there was a bug resulting in unlimited Bitcoin creation."
This is the type of thing that worries me most about crypto land and open source in general. While NEM has what appears to be a great partnership with Mijin and Dragonfly, my hope is that NEM is always aware of, and approves of the features and implementations that these projects expose in the wild. This is especially important because this is a publicly acknowledged relationship, and any failures will have the NEM chain at it's root. On the other hand, any hack can poorly implement (or intentionally poorly implement) the NEM chain to cast doubts on the platform. I understand that these relationships are necessary for growth and wide spread adoption. I just wish there was more controls in place that could protect the hard work that this dev team has accomplished.