I'm assuming no one can actually tell I'm using LibreOffice.

Trace formatting issues aside, it will show up in other subtle ways such as smaller *.docx files and cleaner doc-to-PDF conversions.

non zero chance at least some of them are, too

I actually had a better time with LibreOffice in school.

There were a number of times professors submitted word docs with instructions in tables that didn't render properly in Word but rendered fine in Libreoffice Writer.

I've also had classes that used csv spreadsheets with a non-comma delimiter. It was very easy to switch the delimiter in Calc. But the professor had to resubmit a xlsx for everyone using excel.