Everything seems to be relayed from Minecraft -> Discord except for actual chat messages. I'm not sure if I have set something up incorrectly, but I have triple checked my config and it seems fine. Chat messages don't seem to be displaying on my server console either.

DiscordIntegration version: 1.12.2-3.0.4
Forge version: 1.12.2-14.23.2.2624
Configuration: gist:discordintegration.json

I have found the source of the issue. I forgot I had a Charset tweak enabled which mutes chat based on distance from the player. The relevant code can be seen below:

pl.asie.charset.module.tweak.chat.CharsetTweakChat.java#L140-L144

The solution would be to use EventPriority#LOW at MinecraftListener.java#L215, and in turn, @asiekierka should be using EventPriority#LOWEST to ensure monitoring and distance culling of messages occurs after any potential modification to the message component has occurred - which is an ideal change regardless of this issue.

What's the point of using distance-based chat if you're just relaying everything to a botnDiscord?

It would be better for me to be able to somehow relay those messages which are not distance-based ("shout" messages) to DiscordIntegration, and back.

Yeah, it doesn't make much sense for distance-based chat.
DiscordIntegration supports IMC messages to allow for sending/receiving Discord messages.

sendRuntimeMessage

Well, that's something I've never heard of. Hm! I might end up supporting this.

Hi, I am running sky factory 4 and I noticed that this same charset mod is included the pack. I have never used or heard of it so how do I disable the localchat distance think without breaking the modpack?