I like your marauders, a funny lot :D Their characters are very good written, just how I imagined! I share your opinion, JK sholud have told us more about the memorable four.. but now, we will never know! It's up to fanfic writters like yourself to create the world of the Messrs! :)
As for your intention to increase our vocabulary, I dont mind, besides my fanaticism for the Harry Potter world, I'm reading fics to "eemprove my EEngliish" ;) .

HungarianWitch

-- “If I do –“ he tried throwing his weight to one side in an attempt to take some of the awkwardness out of his position “ – manage to get out of this – irk – predicament…I don’t want to have to – ugh – explain to Madam Pomphrey how I managed to – irk – splinch myself in a place that you can’t even Apparate.”

lol. I think it's amusing how the quotes don't go the right way sometimes, especially after a hyphen. XD And "Pomphrey"? Don't you mean "Pomfrey"?

And I particularly *loved* how the Map was coming along. XD And that changing-the-rules bit too.

-- “My mother said you are also welcome back as long as you leave her tea cups along this time,” Remus said pointedly, sighing a bit, “She told me that the novelty of having to run and catch them wore off a week after your visit ended.”

Tea cups "alone"?

-- “Dad reckons he could beat you at Exploding Snap next time you came.”

Next time you come? This one was actually a bit "eh" because now I'm not so sure whether it's "came" or "come". Blah.

And tricking Slughorn into thinking that Peter was the master mind? *Genius*

this was really fun! i kind of wanted snape to make an appearance, but oh well.

Oh my goodness, I must say I absolutely loved it. Sirius is so fantastically awesome, it's not even funny. He's also my favourite. I especially loved his reaction after the howler had opened and all his bows, and I liked Dumbledore nodding politely back. Who am I kidding? I liked the whole darn fic so very much. I think you captured each of the marauders splendidly and I really and truly love it. No critiques, it's just pure awesomeness. You write very cleverly, thank you for writing this story.

*grins* This is great - I really like the way you show the groups as a whole, and Sirius is awesome XD

That was cute. Great job!