The ability to tie contributions to individual user profiles can help to:
Making it clear to users that their contributions are not anonymous might also encourage them to contribute in a more productive and considerate manner.
One downside of requiring users to register to contribute to a project is that it adds friction. But this might be lessened by providing a good Onboarding Process.
The other major downside of relating contributions to individual user accounts is that there are increased privacy risks. For example contributors might be incidentally giving away personal information, e.g. home or work location, as a side effect of contributing to the project or Submitting Evidence.
Ensure you are minimising the amount of data collected from contributors and that sensitive information is only shared as required. Ensure that you are complying with appropriate data protection laws and regulation, e.g the GDPR.