These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Badass Decay: Oh god yes, he started out as an uber heel that murdered everyone, beat John Cena for the WWE Championship, "retired"Triple H and dominated most people he's been up against, as soon as he won the championship a second time he's really started to loose all the badass cred, Randy Orton punked him out whenever they faced each other (to this day Sheamus has never beaten Orton), he ran like a bitch from The Nexus, hell, The Miz kicked his ass.
Recently, he's forcing the Badassery to re-emerge. Talking trash with Randy Orton? Check. Classic triple threat match with Mark Henry and Christian? Check. Recovering from THE PUNT in ONE WEEK? CHECK. Interrupting the Randy Orton / Christian contract signing and punking out both men? CHECK. The audience is now seeing how Sheamus is a force to be reckoned with. This has led to Sheamus actually being cheered! Heel-Face Turn fast approaching?
Taking on Mark Henry, because no one else want due to him being on a warpath and taking out a bunch of people. And getting cheering for it. I would say YES, most definitely approaching a Heel-Face Turn.
Withstanding the Great Khali vicegrip and Breaking out of it.
Many people also consider his face character to be this all-around. In any actual feuds, Sheamus usually isn't that much more morally right than his heel opponents, and will sometimes attack his opponents mostly or entirely unprovoked.
Fridge Logic: The commentators regularly state that growing up, Sheamus was bullied for having pale skin and red hair. Aside from only stating this because he's now the face of the Be A Star anti-bullying campaign (which in itself is Fridge Logic because his character started out as a notorious bully and even as a face has the Hair-Trigger Temper to pass as one), Sheamus is from Ireland, with a great many Irish people having red hair and pale skin.
Internet Backdraft: Involved in one after his Squash Match against Daniel Bryan at Wrestlemania 28. Curiously, most of the ire seems to be less about the fact Sheamus won, as pretty much everyone and their mother figured Sheamus would come out that match the victor, and more that the match took 18 seconds, although the backdraft wouldn't be as bad if Bryan won in 18 seconds rather than Sheamus..
Misblamed: He's been forced to endure some vicious booing for that booking decision in the week(s) directly following Wrestlemania - for a booking decision that wasn't his fault, natch. The whole incident came dangerously close to derailing his title run, but thankfully it's mostly gone after he faced Daniel Bryan at Extreme Rules in a two out of three falls rematch and worked his ass off, keeping up with Bryan in a well received match.
Notably, no one seems to know what to call this move. Sometimes Colewill call it the "Celtic Cross". The next week, it'll be the "High Cross." Before either of those, the move was briefly called "Pale Justice", which arguably might fit better now than either of the first two, given Sheamus' new "Great White" Red Baron and his status as a Face. As of right now, the announcers seem to be settling on "Celtic Cross".
And now, ironically, Sheamus has added to his moveset the finisher that Finlay calls "The Celtic Cross." Only, for Sheamus, it's called "White Noise."
A more literal example of the trope: Sheamus got himself into one of those "your Finishing Move is banned" scenarios with a Rules Lawyer-ing Alberto Del Rio. Sheamus even began using a new submission finisher around this time to foreshadow and then 'sell' the ban. But when the time came for the match, perhaps finding out that Del Rio's sidekick was overselling the injuries to his neck, Booker T reinstated the Brogue Kick, rendering the whole plotline null and void.
Unfortunate Implications: Sheamus referring to himself as the "great white (shark)" when confronting Scary Black Man Mark Henry. Even better, the nickname stuck and the commentators now refer to him as such.
The High Cross is a crucifix powerbomb.
He's nicknamed the Great White, he uses cross imagery and his minitron during his entrance contains fire. Great White, crosses and fire... you'd think WWE would've thought that through a little better.
Although in their defense, people wouldn't be thinking along those lines by virtue of Sheamus being Irish and not American.
Also, it can be argued that the nicknamed refers to his incredibly pale complexion.