Linux

Firstly, there's no guarantee that a document would look exactly the same even within different versions of MS Office itself. Also, try opening any complex document in MS Office on macOS for instance, and you'll most likely notice issues or differences compared to the Windows version. In my old sysadmin job, where I used a Mac, we had a standard "change control" template that we had to fill out when doing infrastructure changes, and the radio buttons used in the form didn't work on the macOS version of Office. So issues like this are pretty common. These sort of issues are why people either normally ignore them OR in the case that layout/formatting is critical (eg: for publishing/printing), then they'd use PDF or TeX or similar formats, where the formatting is preserved.

Secondly, as @[email protected] mentioned, use OnlyOffice if MSO compatibility is important. Below is a screenshot I captured of a recreated Lorem Ipsum docx on my Linux machine, with MS Office Online (running on Edge) on the left and OnlyOffice on the right.

As you can see, they're virtually identical - and any difference in the sizing etc would come down to the fact that I'm running the web version of MSO, so the zoom/scaling may not exactly match that of OO. But other than that, if you check the spacing and everything else, it's pretty accurate.

Finally, in saying that, even OO has it's limitations and isn't a 100% replacement for MSO - as it can't run macros, or may not be able to display certain types of embedded objects in Excel and so on. But then, even the web and Mac versions of MS Office has these sort of limitations. But the average home user wouldn't normally use macros or advanced features in Office, so for the most part, OO, or even LO should be fine for most users.

Also, just as a reminder, in this thread we're discussing about how Linux can work fine for most home users, the kind of users who have simple requirements, and aren't dependent on specific proprietary programs like Photoshop etc. Obviously Linux will not be suitable for every single need or use case out there, but neither is Windows or MacOS - if you have special needs or requirements, then use the tool that's best for the job. But nitpicking minor differences like this isn't helping anyone, we'd be sitting here arguing all day about how "X OS sucks because it can't do Y", which is a pointless exercise.

Edit: I was curious to see how bad LibreOffice actually was so I just tested it out:

... and that was surprisingly not bad at all! Just one word out of place. But this goes to show how opensource software is ever evolving and constantly improving - so a particular criticisms you may have had in the past may no longer be applicable, unless you test it out yourself against the latest versions.

Use OnlyOffice if looking like MS Office is that important.

Different people have different workflows. Documents is something I create using LaTeX and Emacs Org Mode. I have almost no use for things like word processors. I spend most of my day in a text editor and using windows would slow Emacs down. I don't expect everyone to work like I do, so you should not assume that everyone uses word processors for their work. Libreoffice Writer is totally sufficient for the rare occurences in which I want to use one. I am the only Linux user at my workplace, all the others use Windows or MacOS and so far I have never used anything except Linux in my professional life. If you need specific features from word, excel or need to install Photoshop or games, I understand your need for a different operating system. My needs are different, I need a system which I can adapt to my wishes.

Doesn't look like a important difference to me, rich text documents are meant to be adaptive. If you want it to look the same everywhere, export to a pdf.