Incorrect MS SQL syntax when COMMENT , ADD, or DROP column

The problem happens on r4390, I have report it to issue tracker: Issue 3179

The incorrect MS SQL ADD/DROP syntax only happen when action on multi-columns, the syntax

ADD ..., ADD ..., ADD ...

should be

ADD ..., ..., ...

Another problem is that the syntax to add comment to table/column, but I'm not sure what is the correct simple way to do that, it seems have to use sp_listextendedproperty, sp_addextendedproperty, sp_updateextendedproperty, and sp_dropextendedproperty on MS SQL?

Sorry for my poor English.