The use of the conjunction "and" leads to an improper assertion about what should/shouldn't be done. Using a semicolon resolves this by indicating the contrasting alternative.
The documentation states that React.renderComponentToString
'uses a callback API to keep the API async', but the
implementation is actually synchronous. In order to maintain
this contract the callback should always be called
asynchronously or be change to a synchronous API.
As per the discussion of pull request 982, the API should
be changed to a synchronous one.