docs: move bsdflags tuning comments to notes docs section

the atime comments are already there.

docs/usage/notes.rst

@@ -61,6 +61,16 @@ affect metadata stream deduplication: if only this timestamp changes between
 backups and is stored into the metadata stream, the metadata stream chunks
 won't deduplicate just because of that.
 
+``--nobsdflags``
+~~~~~~~~~~~~~~~~
+
+You can use this to not query and store (or not extract and set) bsdflags -
+in case you don't need them or if they are broken somehow for your fs.
+
+On Linux, dealing with the bsflags needs some additional syscalls.
+Especially when dealing with lots of small files, this causes a noticable
+overhead, so you can use this option also for speeding up operations.
+
 ``--umask``
 ~~~~~~~~~~~
 

src/borg/archiver.py

@@ -2761,12 +2761,6 @@ class Archiver:
           it had before a content change happened. This can be used maliciously as well as
           well-meant, but in both cases mtime based cache modes can be problematic.
 
-        By default, borg tries to archive all metadata that it supports archiving.
-        If that is not what you want or need, there are some tuning options:
-
-        - --nobsdflags (getting bsdflags has a speed penalty under Linux)
-        - --noatime (if atime changes frequently, the metadata stream will dedup badly)
-
         The mount points of filesystems or filesystem snapshots should be the same for every
         creation of a new archive to ensure fast operation. This is because the file cache that
         is used to determine changed files quickly uses absolute filenames.