Why does this batch file fail on a "REM" line?

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Chapters
00:00 Question
02:25 Accepted answer (Score 52)
03:39 Answer 2 (Score 11)
04:06 Answer 3 (Score 10)
05:14 Answer 4 (Score 0)
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Full question
https://superuser.com/questions/1610492/...

Question links:
[Add text to end of filename (but before extension) using batch file]: https://superuser.com/questions/603958/a...
[as provided by @Karan]: https://superuser.com/a/604285/489136

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Tags
#windows #commandline #batch #batchfile #comments

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