Contractions - could've

Open Office makes a little wiggly under this contraction basically saying to change it. But is could've not acceptable in writing? I don't mean dialogue but I typed in this sentence - Dexter could've sworn the eyes moved.
And Open Office flagged it. I don't always take everything it says as a rule but I found it strange. Should it be switched to - Dexter could have sworn the eyes moved?

 

It's perfectly acceptable. Programs like Word often make mistakes when it comes to pointing out grammatical errors.

 

Yeah, that's perfectly fine. Not sure why it would balk at could've. Word always gripes when I use the word same in the context of: ... having been explained of same during the prior hearing. It's a common bit of legalese that comes up all the time in court docs, but Word clucks its Microsoft tongue. *shrug*

 

You can probably try to disable this in your spell check settings if it is calling you out on grammar/style rather than spelling; otherwise, you can add it to the dictionary. Microsoft Office has a feature to check or ignore contractions, so maybe Open Office has it too. I have only ever used Open Office like...once until I decided that I hated it.

I like to enable most of the style checks just to keep me aware of what I am writing.

 

My version of Word doesn't flag it.

 

Well my character is Will and whenever I write something like: "Will walked down the street," 'Will' gets flagged with a squiggly green line lol.

I use could've all the time, actually. I'm not sure if it's an official contraction like you're though, is it?

 

I'm using LibreOffice (which is based on the same framework as OpenOffice) and it doesn't complain about "could've".

 

I wouldn't use could've in the narration, although I think it's fine when writing dialogue. It isn't incorrect per se, but I personally don't like the look of it and don't think it's commonly used.

 

I agree with this, but I've never had a character who would talk like that!

 

I wouldn't use could've in a formal voice. It would be fine in the narrative of some novels. It would be entirely natural in dialogue. But, yes, in my own fictional narrative I would probably use "Dexter could have..." unless I was very tightly inside a character's voice.