Because being tight is considered a beauty standard for women, not so much for men. For men this is mostly upper body muscle (shoulder, arms). A vest top would he an equivalent, and you don’t see skinny guys wearing that either.

I don’t think any of the algorithm is expose to other instances so that wouldn’t impact the communication between instances. At the end of the day this is open source so admins can freely build a forked version of Lemmy with a slightly different algorithm.

There might be things Meta isn’t allowed to do with WhatsApp. Also the concept of account is bit blurry on WhatsApp because you basically login with your phone number and an SMS code sent to your device. This wouldn’t work as well for a service that can be used elsewhere.