I can confirm I am still experiencing this exact issue and have been for the last few years. After attempting to sign in with a Microsoft Account, I am returned to the main page of the Feedback Site still not signed in. This issue persists across all devices and browsers I have attempted with.
The Microsoft Account I am using does show the Feedback Site as an external app I have successfully given access.
I remember 1.13 was the first time I really noticed this issue, and it seems to generally have gotten worse with each update. 1.18.2 seems slightly improved in some cases when compared to 1.18.1, though.
I'm also having the same problem on iOS with version 1.6.0. I've tried restarting, reinstalling, relogging, testing on a variety of different wi-fi networks. I bought minecraft specifically to play with my friend and since that doesn't work, it's completely useless to me.
At this point, I'm charging back Minecraft as Microsoft doesn't seem to care about this issue anymore. I suggest anyone who is having this issue to do the same.
iOS: https://support.apple.com/en-us/HT204084
Windows/Xbox: https://support.microsoft.com/en-us/help/10558/microsoft-account-refunds-for-purchases-and-subscriptions
If none of these work, contact your bank and dispute the charge.
If you buy something and you're led to believe it should work a certain way and it doesn't, you are entitled to a refund.
@kcobb0807, I'm having the exact same issue. I'm not the Realm owner, but everyone else in the Realm can write on signs, chat, and see each other's messages. They cannot see anything I type in chat and my messages on signs disappear when I place them.