* LeBoOo sets mode: -meo LeBoOo
This shows up when the server sends the modes to mIRC (see for yourself with /debug -pt @debug); the server sends the modes to you even if you set them (unlike messages you send). mIRC assumes that channel mode e takes an argument (as it usually does), so "LeBoOo" is used for that. There are no arguments left to apply to channel mode o, so mIRC doesn't know who was deopped.
The server needs to send CHANMODES, since it is using an unusual meaning for channel mode e.