After installing the latest release of MsgPlus! I found the feature I was looking for for a long time: the ability to set custom names, and appending the nick a person has set.

But I found out that if I set it to only show in the contact list, and not in conversations, that smilie-codes aren't changed to the smilie-images when a contact sends a message.
And also the StuffPlug-NG plugin fails to make urls clickable.

But, if a contact closes his message-window, I get a message (enabled in StuffPlug-NG) and strangely enough the smilie-codes are changed into smilie-images in those lines.

So I just want the smilies back
Such a shame of such a wonderful feature...
Or am I missing something?

This is a known limitation in custom names, that has been there since they where introduced.
The reason for this is that plus changes the contact list to "view by email" so it can show the custom names, and messenger doesnt parse email addresses for emoticons.

But why is there a difference between ':D nick :D says: ' and ' nick has left the conversation' ??

but it's a shame though.. ahh well, It was too good to be true..

because it's Messenger that does 'has left the conversation' messages, Stuffplug NG just enables them