Well, it's not as much of a bug, but as a user interface issue.
Some people swear on their life their OE's IMAP support is rock solid.
You said by yourself that OE has serious protocol violations.
Only some versions of OE are crippled. OE's really not OE. Lots of stuff
OE does is actually part of MSIE; installing MS Office also installs some
libraries that are shared with OE. Depending on the particular combination
of the official OE version, MSIE version, Windows version, current+previous
service packs, Office version, and gawd knows what else, you'll see widely
different behavior from the OE client.