When I fetch a favicon with this plugin, the Last Modification Time is not updated on the entry that now has a changed favicon.
The main reason this is a problem is because I use "Synchronize", and when I do, those new favicon links are severed again, because the synchronize mechanism doesn't see there is a recent change.
A manual workaround is to open the entry, "edit" the favicon by hand, and not actually change it but close the dialog again. This does update, but has to be done by hand for each entry that is affected this way.
I love this plugin, it is very useful, but I'm struggling with this misbehavior.
I've just released version 1.6 which updates the modification timestamp when it has downloaded a new favicon.
Note that no new history entry is created becuase:
a) I think it's probably overkill for a mainly cosmetic piece of data
b) I'm not sure how to do it yet!
I hope this helps your workflow.