A few things:

1) The Command Line for this entry is incorrect:
https://mariadb.com/kb/en/storage-engine-independent-column-compression/

{{column_compression_zlib_level
Commandline: --column-compression-threshold=#}}

Needs to say "zlib-level" (I suppose).

2) Could it be added to the documentation of that page, or at least clarified here,
whether does it make sense to do Column-level Compression, if PAGE_COMPRESSED=1 on that Table?

Meaning, use "PAGE_COMPRESSED=1" and "COMPRESSED" on a blob column, at the same time on the same table, does that make sense, or would PAGE_COMPRESSED=1 be enough?

3) A big advantage of using PAGE_COMPRESSED is that the compressed data won't be cached in the buffer pool. What's the case for Column COMPRESSED?
(would be nice to have that in the documentation too)

Thank you very much.