Originally Posted by kovidgoyal
You're saying this happens only for the custom comments edit box and not the builtin one?
Correct - only custom Comments in the standalone editor - not custom or standard comments in the Metadata editor.
You may recall the frustrations I expressed with Metadata Edit and its layout of Custom Comment columns at launchpad.
That was solved when I discovered I could have custom comments shown in the spreadsheet, that I could edit them by pressing F2, and I could make them look half decent by hiding them behind column icons with no text. Incidentally I regard this feature of calibre as manna from heaven - I now only use the bulk Metadata Editor.
Had I known that in trying to get rid of the pesky html snippet pastes that I would, as a consequence (not as a cause), lose my column icons I wouldn't have bothered