Most user friendly syntax for template variables

Is there any research or any winning standard on what is the most user-friendly syntax for template variables?

Or any other grounded opinions about this subject? I.e. capitalization or escaping of symbols.

My company is {companyName}. My company is <companyName>. My company is [CompanyName]. My company is *|COMPNAME|*. (MailChimp) My company is %%company_name%%. (SalesForce) My company is {{ company_name }} (HubSpot) 

I know it’s a small thing, but I guess it can’t hurt to slowly strive to more standards.