mastodon.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
The original server operated by the Mastodon gGmbH non-profit

Administered by:

Server stats:

354K
active users

⚠️ We are planning to release important security fixes for on July 6th, between 13:00 and 15:00 UTC. They will be available for the 4.1, 4.0 and 3.5 versions as well as a nightly release, to make the upgrade as small and painless for everyone as possible. Be ready to upgrade!

@arunshah240 @Mastodon direct message does exist as a privacy option for each message, alongside public, unlisted and followers-only.

Quote-posting isn't in plans for Mastodon, but exists in other compatible options, like Calckey, which some instances use.

You can already direct message people on Mastodon!

But I agree, it needs an WebRTC-esque chat that’s compatible with Pleroma, Akkoma, and all the other Fedi platforms that have already implemented it.