Right now, if you use If and have a then parameter, the template looks odd, since else isn't in the same nesting and indentation level as the then part. Example:
A then parameter would allow everything to be in the same nesting and indentation level. Example:
If then is missing, everything works as in the past (if test is true, render the body of the If except for the else block; otherwise, render the else block). If then is present, everything outside then and else won't appear regardless of the test being true or false.
else should also be present in the Unless component, since it and If have almost all their logic inherited from AbstractConditional, their superclass.