Digitalocean should consider adding support for underscore subdomains.
I raise this suggestion because I just ran into trouble of underscore sudomain.
Since most DNS service provider support underscore subdomains, I don't think it cause any issue.
But the problem is as follow:
A records with underscore subdomain will resulted termination of zone file, meaning that the subsequent records will not be processed.
If there is an issue implementing it, a input validation should be implemented to prevent a small mistake resulted into a bigger problem.
Sorry for my poor English.