So, we arrive at the end of this progress. Several things are uncovered: let's look at them.

Summary

Darcy has gone from (as far as we see) inarticulately proud, even arrogant; ignoring, even not above insulting the people around him, mostly silent, solemn.

He progresses (through his budding interest in Lizzy) to listening to her conversation, to attempting to speak to her, giving up easily when she rebuffs him, but never apparently understanding why he's being rebuffed.

We hear (second-hand) that he can talk easily enough to friends (I deliberately discount Wickham's sneer); we hear him criticized for not being willing to talk openly; we hear his reply that he's unable to do it easily. I repeat that I believe him; the pair who so easily criticize him are themselves easy and confident talkers.

I have commented in my previous Progress reports and in other threads, and have at times been criticized for ignoring:

• his apparent "well-spoken" facility during the first Proposal (ch. 34)
  
• his skill with the written word the next day (ch. 35)
  
• his apparent facility with the Gardiners. (chs. 43, 44, 52)
  

I repeat here my replies that

• He had been working, maybe for several weeks, to prepare himself for this proposal, and even though it spilled out accidentally (I'm convinced), its substance was ready to go
  
• He was already known to us to be comfortable with the written word; he'd had all night after the Proposal to work on it and refine it
  
• In his initial contact with Lizzy and the Gardiners he was utterly inarticulate and fled quickly
  
• When he returned to them for the second meeting at Pemberley he'd had some considerable time to compose himself and prepare his addresses to the group
  
• The Gardiners, being good, polite people would have encouraged his addresses without attempting to challenge him on any matter on his home turf
  
• He would have taken the initiative to guide conversation in directions comfortable to him
  
• At Gracechurch Street, he came prepared and ready to deal in a matter he was definitely competent in -- business (even such a business as this)
  

Sixth Week

chapter 53
Darcy is again tongue-tied -- but this time, notice that Lizzy is, too: She was in no humour for conversation with anyone but himself; and to him she had hardly courage to speak. She doesn't know where she stands, and wants very much to be in good (the best!) standing with him.

chapter 54
Darcy is again tongue-tied -- as, again, is Lizzy:

• Anxious and uneasy, the period which passed in the drawing-room, before the gentlemen came, was wearisome and dull to a degree that almost made her uncivil.
  
• Darcy arrives with the gentlemen; after she tries one sentence to start a conversation, She could think of nothing more to say.
  
• When she's unable to continue without his help, and another girl speaks to her, he gives up -- again.
  

We're pretty sure he talks to others during the evening, but we're given no indication how easily or confidently.

Dary disappears again until Lady Catherine attacks Lizzy (ch. 56), then, upon getting no satisfaction from her, him. He hastens to Longbourn, where Lizzy is burdened with the task of entertaining Darcy so Bingley and Jane can be alone. Upon Lizzy's revelation that she knows how Lydia's affair was cleaned up, he again proposes -- sort of -- and she accepts -- sort of. :-)

Now confident of her love, he begins to open up, confessing his conviction that she had been right; that her outburst had first angered him, then caused him to think about it, then accept the truth of her reproofs, then address them.

The rest of the story shows Darcy just as inarticulate as ever, but no longer offensive. Maybe he's even practicing, as Lizzy and Col. Fitzwilliam advised. Maybe he has been practicing ever since Rosings. I like to think so, even though it hasn't yet made much difference in his general "conversability".