As a Roblox developer/user, it is currently too hard to totally block out a person who harasses and targets you.
Currently all the block feature does is block the user on that ONE account, this means they can create an alt (or get on a different account) and follow you straight back into the game and continue doing what they were doing that caused you to block them.
If Roblox is able to address this issue, it would improve my experience because the community would be safer and it would greatly improve the blocking feature.
This feature has been suggested before, but mostly in the context of using IPs (not mentioning this in the feature request is good - these threads are more for what, not how). This problem is very interesting because IPs are very good for blocking in some cases, but have some major caveats:
Homes can share IP addresses because there is more internet-connected devices in the world than there are IPv4 addresses (~4 billion). If you IP ban someone misbehaving, you can potentially ban family members who did nothing wrong.
Mobile devices on mobile networks frequently change their IP addresses as they disconnect and reconnect from cell towers.
Proxies can mask your IP address. If someone is wanting to harass you, they would probably use at least 1 proxy, and probably from a provider that has several problems.
This would be a very good feature to have from a stance of protecting kids from extreme harassment. Solving this problem would be pretty difficult though.