"REM" is a batch command which gets executed even if there is no comment.
Salmon Trout just proved you wrong. If it was treated like any other batch command, the "remtest.txt" file should have existed. As he clearly shows the file does not exist, so redirection does NOT occur with REM.
"::" is a place marker with the name ":". unless there is a "GOTO" command that references it, it will be completely ignored.
And this is why you shouldn't use it. Try using it in a nested for or if statement and tell us how successful you are.
use "::" for multiline comments. REM will slow down the batchfile.
I'm sorry, there are two things you're misunderstanding here:
First, there is NO multiline comment for batch. a multiline comment is something like /* and */ used to delimit C++/C#, java, etc multiline comments, or { and } in Pascal, and various convolutions in other languages. everything is ignored from the starting character until it finds the ending character. There is no equivalent construct in batch.
Also try using your pretend comment ( :: ) within a batch file using NT command extensions and nested blocks.
Secondly, if REM can slow a batch file down enough to matter, then you should be using batch in the first place.