Hashtags on Twitter aren't case sensitive. So #happyeaster, #HAPPYEASTER and #HappyEaster are all, as far as Twitter is concerned, one and the same.
If you were a brand using this hashtag, you might opt for the #HappyEaster variant because the initial caps indicate the start of each word and help with readability. That's fine, but be careful not to choose a hashtag that requires initial caps in order to be unambiguous.
A case in point is the #DadsCare hashtag currently being used by Dove Men+Care (@DoveMenUK), the men's toiletries range from personal care brand Dove. The sentiment behind #DadsCare is admirable, celebrating all the dads caring for and entertaining children during lockdown. It's something I can relate to on a personal level!
Whenever Dove tweet about this, they are careful to use the initial caps (or so-called 'camel case') variant: #DadsCare. But my first encounter with it, via a promoted tweet, was rather different:
Without the initial caps, my brain parsed the hashtag in the image as 'dad scare'. 'Share your dad scare videos' - what on earth is a dad scare? Is it dads scaring their kids, or kids scaring their dads? Perhaps Dove is telling me that my deodorant will keep me, a father, fragrant after a massive fright?
I'm not sure why this image uses the hashtag in upper case when Dove is otherwise careful to use camel case. Perhaps it was created by a different employee, or maybe an external agency? I can only speculate.
But it does help to illustrate a wider problem. As soon as you adopt a hashtag, it takes on a life of its own and you lose control over its usage. Not just over who uses it, but how - including the case they put it in. And if you can't achieve consistency in your own marketing material, there's no way you can expect consistency from your audience either.
So your hashtag shouldn't be ambiguous when written in any case. If it is, then you will either confuse your audience, or - perhaps worse - they will become aware of the ambiguity and start talking about your hashtag for the wrong reasons:
Oh, Dove. #DadScare 🙄
— Blocks (@AllYourBlocks) May 7, 2020
— phweakazoid (@Phweakazoid) May 8, 2020
— Matthew (@rubberplantguru) May 6, 2020