would be interesting if the voice chat is the joint effort done with Discord
https://discordapp.com/features
A page ago Nintendo was asking you to use a splitter to merge smartphone audio with the Switch for voice chat, I highly highly doubt they'd be capable of tying up with Discord.
In terms of literally anything to do with online functionality, just assume that nintendo is 10 years behind, and maybe add on another 3-4 years just to be safe.
the Switch has done so many things right since launch, and if you've followed Nintendo you'd never expect them to innovate with regards to their online service, but...this. In 2017. Using a smartphone app, a Switch and mushing the audio together with a cheap splitter\merger\whatever completely boggles the mind. IN 2017. also, this setup is obviously meant for handheld play. If you only play docked and want to chat online? Good f'in luck, mate.
Sony has pretty much the same problem with the PS4, where its Bluetooth chip is locked down, but it at least has a varied enough ecosystem where you can pick between a bunch of wireless headsets. Nothing like this exists for the Switch.
Unless Nintendo pulls something miraculous out of its hat this E3 to address the voice comms issue, voice chat for online play, which is something people have taken for granted on PC/PS4/XB1, will only be a very niche thing on the Switch.