Well, I really like the new private messages - it was long time overdue. But I see a few problems in the implementation because chatters are able to bypass all the chat restrictions and the only way to block the messages does not affect the chat. This system is rather new and most trolls haven’t thought about the possiblities of that. However once they did that, we will be in deep trouble. 
1st scenario:
If I wanted to troll someones chat the first step would be to make the moderators ignore me. Because once they ignored me I can spam the chat as I want because there is nobody that can stop me from that. Or if they do not ignore me, I would keep them busy by sending a lot of useless private messages to fill their chat. Another problem is, ignoring and unignoring people is a pain as you have to type in everything manually especially when the chat moves fast or the sender is in another chat. You can’t even see who is ignored and who is not. BTW. when will this feature finally be added?
2nd scenario:
Instead of posting e. g. “boob request” or other insults in chat, people can just send them via whisper to the streamer. Moderators can’t do anything about it which means that the streamer has to stop the game to ignore single accounts. If it is just one, all right. If there are a few dozens, it will be a pain in the butt. Besides that, just because they are ignored doesn’t mean they are banned from the chat and the other way around. Once you have ignored them and you forgot to keep them from your chat, see 1st scenario.
Solutions atm are just to use another chat client. This will make you ignore all private messages, but the downside is, you cannot use the possibilities of this and even if someone sends you something private that is important, he will never know that you haven’t read it because there is no receiving confirmation. Another solution would be to use a customized chat that implements for example all the filters regarding links, blacklisted words, messages you can receive within a certain time, all the things we have in chat with our bots now. The problem is, most streamers don’t have the possiblity to implement that or people that could implement that for them. I built a system like that and believe me it is not as trivial as it sounds with the poor tools we have now.
So my suggestions would be:
- Add a channel context and the possibility to restrict the context (e. g. people can only send me private messages from my channel)
- Extend timeouts/bans to private messages. That means, if someone is timed out for a certain amount of time from a chat, he cannot send any private messages from this channel or to this channel.
- Go away from the ignore system or make it at least usable (e. g. at least a list of people that are ignored).
- Give us the possibility to share our private messages with other accounts e. g. to bots that can check the content and decide wether it is e. g. appropriate or not and if not clear the messages like we can do in chat now.
Then the private messages will be awesome. 