It looks like that file starts with a UTF-8 BOM (Byte Order Mark).
This is what a hexdump of the file looks like:
$ xxd ./Alienation.md
00000000: efbb bf2d 2d2d 0a74 6974 6c65 3a20 416c ...---.title: Al
00000010: 6965 6e61 7469 6f6e 0a74 6167 733a 0a20 ienation.tags:.
00000020: 202d 2063 6170 6974 616c 6973 6d0a 2020 - capitalism.
00000030: 2d20 616c 6965 6e61 7469 6f6e 0a2d 2d2d - alienation.---
00000040: 0a0a 5468 6973 2069 7320 6120 6e6f 7465 ..This is a note
00000050: 2e .
Notice that the first three bytes are ef bb bf
and that the ---
starts at byte 4.
As can be seen in the source code, Joplin expects the first characters of a YAML frontmatter note to be ---
, and it seems that the BOM is breaking that assumption.
Edit: I've created a GitHub issue.