Haven't been able to reproduce the data overwrite problem, but I did add sanity-checks so the save will refuse to run if you're looking at someone else's data, and indeed, even if you manually go in and re-enable the save button (which disappears when showing someone else's data), it won't work.
Also added a feature to LibMerisioux to delete old error/timeout entries, which reduced the size of my SavedVariables file by about 75%.
PLEASE BACK UP YOUR SAVED VARIABLES FILE BEFORE RUNNING THIS. There's a deletion of data involved, and while I tried super hard to be paranoid about it, it's possible that it'll screw up. It does tag the data of any character you log in on as "self" data and won't delete that. I think.
Still thinking about a UI for letting you browse, and possibly search, characters and descriptions you've seen. I want to do one, but haven't figured out what it should look like.
If you've been bitten by the override bug: If you could grab the LibMerisioux.lua file from your saved variables directory (Interface/Saved/SavedVariables), zip it up, and email it to me, that would be super handy, I could maybe figure something out. Let me know which character you were on that got overwritten.