I'd like to suggest two things.
First, echoing Grizzly. If your character can't understand what another character is saying (either when reading it or having a screen reader read it to you), deal with it ICly. Tell them you don't understand. Nod and smile. Any one of the many things people do IRL when they can't understand someone they are speaking with. It's good RP.
Second, instead of listing how YOU feel people are doing accents wrong, list ideas on how you think it could be cool to do an XXXX accent. Like:
Uneducated Street:
Mix and match some of the following elements.
Use 'got' as often as you can instead of 'have': I got ten bucks to my name!
Combine to and leading words: 'bunch of' becomes 'buncha'. 'Lots of' becomes 'lotta'. 'Got to' becomes 'gotta'.
Use the wrong verb tense: 'He were there' instead of 'He was there'
Drip the trailing G in most cases (sometimes adding an '): I was lookin' for you.
Replace long 'oo' (like 'to') with 'uh' or 'a': I want tuh see yuh later.
Replace 'er' sounds with 'a' or 'uh': Let's do it togetha.
Always choose the simple word: "You're pronouncing that wrong!" becomes "You aren't sayin' that right!"
Use 'ain't' often: I ain't know. You ain't where you're supposed to be.
Use all the contractions: 'He is quick.' sounds smarter than 'He's quick.'
The fact is that there is no right or wrong way to do any particular accent. But throwing out suggestions on how you think a particular accent could be done might help others and is far more constructive that asking people to stop doing things you don't like.