Highly recommend https://wpmudev.com/. Source: 12 months ago

WPMUDEV is a plugin developer and hosting provider, you're probably thinking of WPML. Source: over 1 year ago

Stop dreaming about tomorrow; start making a difference today. Join our team at WPMU DEV and be the hero you’ve always known yourself to be! Source: almost 2 years ago

A great resource for hosting multisites is WPMUDev since they support it on all their hosting tiers and comes with a wildcard SSL cert for HTTPS on all your sites. If you haven't set up a multisite before, I highly recommend going with WPMUDev since their support team will literally just do all the work of setting it up for you if needed. Source: over 2 years ago

I use Forminator by WPMU DEV. Its free plan allows us to add "upload file" block. But, yeah, it's still vulnerable in case someone upload malicious file via it. Forminator can be combined with Akismet & Captcha (to block spam bot), and WPMU DEV also has security plugin named Defender. And lots of good hosting includes ImunivyAV/360 into FTP. Source: over 2 years ago

Https://curius.app/ fills this niche for me (not affiliated, but have quite enjoyed it). - Source: Hacker News / 6 months ago

Though you can't respond to others comments for now, but thank you for voicing the interest in that! There are some other extensions that provide just the commenting part (e.g. https://web.hypothes.is/, https://curius.app/, https://glasp.co/), but I find that they suffer from the cold start problem. - Source: Hacker News / over 2 years ago