Can Mac OS 10.8.3 and 10.6.8 share the same User/Home folder?

Question

I use both OS 10.6.8 on HD and 10.8.3 (on a SSD). Most of my User data is on the 10.6.8 drives.
Presently I manually save data when using 10.8.3 to the 10.6.8 User folder. I know I can select Advanced Options in System Prefs in my Accounts folder to make the 10.6.8 User folder the User folder that 10.8.3 uses.
If I do that can I alternate booting from one OS to the other using the same User folder? Or is there a problem with both OS's writing stuff to the
~/Home/Library folder that may be incompatible? Or to other places I'm not aware of?
I have more than enough space on the SSD to partition it for both OS's (now only 10.8.3) and both Applications folders -  to speedup whichever OS I need to use.
To have one User folder for both OS's would save a lot of drive space and make backing up much easier and faster. But I'm also not sure how I'd use Time machine with such a set up. Presently I backup with Time machine plus clones to other HD's. I'm totally confused by all this and wonder if someone out there has used the same User folder for different OS's.
Grateful for any advise.
Thanks,
MartyP

Answer 1

MartyP wrote:
Or is there a problem with both OS's writing stuff to the
~/Home/Library folder that may be incompatible?
Yes, big time.  Mail, for sure, has a different file/folder structure, and would not be happy.
Plus, a number of apps (Apple and 3rd-party) are "Sandboxed."  That's a security feature, to prevent malware or bad coding from affecting things it shouldn't.  Some of their files, including the preferences files, aren't even stored in the same places!
Or to other places I'm not aware of?
Probably.  If you have two versions of the same app, they may or may not expect the same data setup.
To have one User folder for both OS's would save a lot of drive space
Not if you use some or all of woodmeister50's suggestions. 
But I'm also not sure how I'd use Time machine with such a set up.
Just as you do now.  By default, Time Machine backs-up everything (except things like system work files, most caches and logs, trash) for all users and all internal drives & partitions.  By default, it excludes external drives.
You can change those defaults, of course, via TM Preferences > Options.
See Time Machine - Frequently Asked Question #32 for details and considerations of multiple drives.
Presently I backup with . . . clones to other HD's
Good.   Yes, clones are different.  You need multiple "tasks" to back up multiple drives/partitions.  But once set up, that shouldn't be a big deal.