allan wrote: I have read that if one installs multiple distros on the same computer that a single /boot partition can be shared between the distros.
Such weirdness is reserved to gurus

And in that post I wrote that you
can do it yes, if you are a guru and know what you do .... not that you
should do it. Notice the difference?
allan wrote: However, when I tried to install Bianca-main as a 2nd distro, with Bianca-KDE as the 1st install, the installer would not let me use the existing /boot partition as /boot for the new install, with the message saying that system partitions such as / and /boot need to be re-formatted. Of course, I wouldn't want to reformat because then I would lose the existing data on the /boot partition.
Of course
allan wrote: Is there anyone who has done this
Yes

And as I wrote in that thread:
This is totally not suggested and not recommended!! You won't get support from anyone if you do this, you are on your own if you hose your system.
allan wrote: that could help identify what I am doing wrong here? Or help with a workaround?
No 
The fact alone that you need help with this means that this topic is waaaay too advanced for you. I'd have to explain too many things
Let's make it simple: If you want to have multiple distros on the same machine you can have them on separate root " / " partitions and share
/home between them without risking too much.
