Webcomic Not Even So Bad, It's Good
I'm not a shipper of Zutara, nor am I a huge fan of the series to begin with. But this is so blatantly going against canon - which is already a pet-peeve of mine. If you don't like canon pairings, fine (I tend to not like them, either), but you could at least try to maintain a certain amount of dignity during.
The characters are all bland, have no personality and are, frankly, idiots. This whole thing is based off of an Idiot Plot.
The art is horrible. While using real photographs of places for background can work alongside drawn character, it doesn't here. The repeated tracing of stills from the show is horrible. It barely allows for movement in the characters, slightly altered facial expressions look like they always convey the wrong emotion and the few times when Diaz actually draws something herself and doesn't trace, it stands out like a sore thumb and looks bad.
Why didn't she just write fanfiction instead of forcing this badly done comic onto the world? Oh, right. Because her lines suck and she doesn't know how to properly spell or seems all that familiar with proper English grammar.
Also, reading the text is difficult. Not just because of the bad grammar, but also because it tends to result in Wall of Text Exposition and no way to make it stand out from the backgrounds properly. I don't know what program was used for this, but it obviously didn't have a 'Stroke' option or something to make the text stand out.
This isn't even a Guilty Pleasure or something to look at, so you can laugh at it and have a good time. It's boring, when it isn't tediously stupid because of stupidity.
Webcomic Absolutely Hysterical
Seriously, you'll laugh all the way to the emergency room as your brain slowly dribbles out your ears.
The wallbangers start off strong right out of the gate with one of my personal favorites: Sokka, trying to comfort his heavily pregnant sister, tells her he thinks their mother would be proud of her. Yeah, you're fifteen (which even for their world is underage) and pregnant with the illegitimate love-child of a head of state. I'm sure mommy would be so proud.
It just gets better from there. From lol worthy mistakes and mishaps like CHARD MONSTER to the painfully obviously traced 'art', you just can't get a better fix for your Bile Fascination.
That said, if you're a fan of the show and really enjoy the deep and interesting characters, go in prepared, because you are about to witness the utter defilement of everything you love about them. You have been warned.
The main page should tell you all you need to know about what else is in store, so I won't retread any of that ground. Just know that there are few things that can compare to How I Became Yours when it comes to unintentional hilarity. I heartily recommend it to anyone who enjoys So Bad Its Good entertainment.
Webcomic Implausable but not Terrible
Having read HIBC I was genuinely expecting it to be an unbearable experience...it's not. No, really, don't let then pearl-clutching and hand-wringing fool you, it's not. Does it shit on characterization? A little. Really, I have to say that, never having been a huge fan of ANY Fire Nation character (but Ty Lee, who is my wifey) I really can't honestly say that they're ALL out of character; Zuko is still a creep with good publicity (and abs) and Mai is still an unironic glorification of everything that made Daria unbearable. Aang and Toph are both still sweet, kind individuals, Katara is still an outright hero, Sokka is largely still a horndog lovable asshole, the biggest changes are Azula (COMPLETE character rewrite) and the actions of Mai to some extent but then again all the Fire Nation folks in the series were just Nazi Party: Red China District. Really, would you put it past ANY of those kooks to kill a baby? Before you answer remember that Zuko burns a town down to find the Avatar once, and he's basically the HERO OF THE SERIES.
Except Ty Lee, she's the breast of them...best of them!
Really I think the reason I enjoyed it more than some was, I have no notion of Zuko being heroic or Mai being a sweet innocent victim, so either one doing something horrible like adultery or murder bothers me not one bit. Also, I love soap operas and the whole thing is so lavish and so dramatic and fantastical it either has to be a parody or straight rip of of soap operas, and the signs are all there.
Love child? Check.
Illicit affair? Check.
Tragic miscarriage? Check.
Forbidden PASSIONS? Check dat.
Evil mistress? Check.
Amnesia? Check.
Nurse my beloved back to Health? Check it before you wreck it.
Cheesy dialogue? GEE YA THINK!
May as well call it Dallas: How I Became J.R's! In fact the exact same plot played out on that show, TWICE, in the reboot and the original series. It's been done three times I know of on One Life To Live, and I lost count on General Hospital. If you like soapy drama it won't bother you more than any other canon-annihilating fanfic. There are far worse, far far worse, so give it a chance...and a rest.