Patrick

> one timestamp per connection is enough Already did that locally, issue still exists.

I took another shot at a plugin that seems to work better: https://github.com/TingPing/plugins/blob/master/HexChat/playback.lua

> @TingPing your most recent playback.lua script worked ok for me, though I still observe replaying messages I've already seen as well. Thanks though this is better than nothing :)...

If it was linked to a different version than hexchat it was just a mistake. Probably a simple fix in the project file: https://github.com/hexchat/hexchat/blob/master/src/fe-gtk/notifications/notifications-winrt.vcxproj

Leave it open its a real bug.

DCC does blocking IO everywhere, it is awful.

Making the move operation async should be easy since it is pretty self contained, making all writes async would be a bit more work.

Any write could still block for too long ofc, so less than ideal.

I also cannot reproduce this bug.

The entire client is broken with non-ascii nicks, so I don't think it makes sense to change tiny details like this to support them.