Is there an English phrase for an inability to actually *leave* already?
Solution 1:
In social work, doorknobbing is the word sometimes used to describe the phenomenon of delaying the important personal revelations until the end of the therapy session when goodbyes are being said.
This option has the advantage of actually being in circulation. It has the disadvantage that it also carries one or two very different meanings of a frank sexual nature.
Solution 2:
I coined a phrase a few years back. I call it conversational dieseling. As those familiar with internal combustion engines will tell you, dieseling happens when a gasoline engine is switched off but enough fuel mixture still gets into the cylinders and ignites from the heat, causing the engine to sputter on. I think it describes the inability to end a conversation (or a meeting) pretty well, if I do say so myself. :)
Solution 3:
To do such is to dilly-dally:
dil·ly-dal·lied, dil·ly-dal·lying, dil·ly-dal·lies
To waste time, especially in indecision; dawdle or vacillate
Informal: to loiter or vacillate
Of note, I think, is the relation to vacillate, that tells us:
To swing indecisively from one course of action or opinion to another.
And then coupled with loiter:
To stand idly about; linger aimlessly.
In context, the optional actions are to talk, or to leave. You're dilly-dallying.
Note: Usage of this might be primarily a UK thing and certainly not exclusive to talking in doorways, but let's see what you and the rest of us think.