so far, so good, though whether i've spoken too soon remains to be seen.
for clarity, the actual process i followed was this;
close all instances of finder.
open terminal.
type in the command as above in my previous post, take heed of the warning about the sudo command.
type in the admin password.
sit back.
now, here is the bit that raises a question or two.
when i did this, i had time machine turned on, but no backup drive connected.
in the terminal window, meanwhile, a prompt repeatedly appears on occasion asking whether to override the permissions on certain .ds_store files, all of which reside in directories found in the mobile backups folder. i said no to each prompt each time.
then, after waiting an age, while the process in terminal was still running, i turned time machine off completely, risky. the terminal process promptly finished, while it responded to no time machine with a repeated message along the lines of directory not found.
expected, as i'd effectively deleted the mobile backups folder.
restarted.
opened a few finder windows, changed the view options, did NOT click set as default anywhere.
turned time machine back on.
that was about 5 hours ago, and no finder view has changed yet.
this is making me think that perhaps the local backups, in particular the local preference backups, have something to do with the view preferences being messed up. or the fact that i left remember windows checked when i restarted.
i'll wait and see some more.