Users with permission to set assignee (responsible person) can automatically set themselves as the assignee (responsible person) when adding new data. This does not affect data modification.

Using this account as an example, permissions can be set for the assignee (responsible person) field in customer data:

When adding new customer data, the responsible person field will be defaulted to yourself and can be modified:

However, when adding a new company, the responsible person will not be defaulted to yourself (since you do not have permission to set the responsible person for a company), and you will not be able to modify it.