I’m not 100% sure, but I suspect this is due to TOR browser’s privacy/security settings.
So it’s not a bug, it’s how it works. The TOR network, and thus the browser was never designed to be everyone, or even a lot of people’s primary way of accessing the internet. It’s meant to keep you anonymous, so I recommend and only use it for things I need anonymity for.
You probably not a high enough trust-level yet. This was done to combat SPAM. To post a URL next time, paste it and wrap it in backticks (``). that will cause it to render like https://google.com.
That is unclear as to why it happens. Just checked and mine does it too. Nevertheless, I still think it’s a setting kind of thing. Not sure. But you shouldn’t worry as, as I mentioned, the TOR network was/is not designed for that kind of usage.
I think it would be better is you tried Vivaldi for twitter if you’re concerned about privacy. I do not know of any other reason to use TOR for twitter, but the fact remains that the TOR network was never designed for and shouldn’t be used for that kind of traffic.