Short answer: replies and voting in live chats is pointless due to the speed of delivery and amount of information that is generated there.
There are two basic yet very important issues when it comes to live chat during streams:
What is a good and what is bad comment?
I have to say that most of the messages you get in a live chat in a stream are garbage. In order to outline good messages first you need to specify what good actually means. And this is the first and biggest problem - how do you define something that in its nature is subjective?
In a live chat with video there are usually three big parties - the streamer (can be multiple), the moderator (can be multiple) and the audience:
- streamer - provides the content. The role is obvious - create the content, present it and interact with the audience
- moderator - the man in the middle. Some think this role is optional but looking around you can see that it's actually become quite mandatory. If present, this is where the bad comments are filtered out. If not present, this task is done by the streamer. However not having an explicit moderator will create a huge burden on the streamer who not only has to provide the content but also take care of all the garbage that is posted in the chat. Moderators need to be invisible
- audience - unless you have just a few people in your audience the amount of comments per second that can be generated is impossible to handle even by multiple moderators. The role here is obvious too - consume the content and interact with the streamer. Sometimes audience can also become a moderator.
A good comment can be viewed by 2 out of the 3 parties as bad (obviously 3 out of 3 is best case scenario but it will probably happen 0.0001% of the duration of the whole stream). If you have a voting system in place what does a thumbs up or thumbs down mean here? Does it reflect the opinion of the audience, the moderator and/or the streamer?
Example: a streamer shows how to place an SMD resistor on a PCB. A problem arises from the fact that it's a female streamer. Some people from the audience won't care about the sex of the streamer. Others will. So rude comments such as "No need for this. Show us your ..." are to be expected. Streamer- and moderator-wise such comments fall into the bad category. But what about the audience - the actual consumer of the content? Should you neglect those who want to see the mounting of the resistor on the PCB or perhaps those who want to see some...flesh?
Naturally basic filters can take care of cursing and insulting but anything beside that is something that only people are currently able to do. And they still suck at it because - as I've written above - the very definition of good and bad is subjective. So moving a chat message to the top of the history since it got voted up the most doesn't actually mean that all parties involved actually think it's a good one.
Even if we know what good is what about the amount of messages and their speed of delivery?
Let's say you have created an elaborate statistical model which defines your perfect audience and anything that doesn't fit is censored in some way (for example message is not outlined as good and thus disappears along the way as the chat history increases).
As mentioned above a streamer has three tasks - content creation, content presentation and interacting with the audience. However these three tasks have very different priorities.
- Content creation and presentation - top priority. Unless the format is Q&A the streamer needs to devote most of his/her attention on these two tasks.
- Interaction with the audience - mid to low priority depending on the stream format. After all the streamer needs to concentrate on the creative and delivery part. If things go the other way, the streamer will be producing a different kind of content which probably is not what the audience is there for.
Even if we have a Q&A stream format the amount of messages (even only the "good" ones) is too big for the streamer to be able to handle. Speed of delivery is also insane. Even a small amount of people can generate a lot of messages. Just watch a live stream chat on YT, Twitch etc. - it's basically a non-stop bombardment, a waterfall of words and (if available) emoticons. How can any human being cope with this insane flow? You will often witness that even people from the audience can't do that. Should a viewer concentrate on the streamer and what he/she is doing or on the chat?
If we get a lot of good messages and outline those somehow we can still create a large enough amount of such messages that it will become difficult to go through. So what's the point?
A comment (like in a forum) is a much better way to ask for and respectively receive information on a certain topic. And even that form isn't without its problems. Things like grammar, way of expression etc. are not something many people view as important when it comes to chat since 1)they have an subconscious expectation that their message will "disappear" (due to the way chat works) and 2)time is of the essence. If you want important knowledge (good messages) to be preserved/outlined in a way, shouldn't their structure also be of good quality?
Adding an additional layer of interaction in such type of chat creates unnecessary overhead. The chances that someone goes through a chat history of over 100 000 messages and says "Hmm, message 458 133 seems like something worthy of remembering!" are slim to none. This is just the way people think.