If you mark a string and press Alt+I,O,F, It will be translated into Equation,but it is not reversible by Ctl+Z.
Created attachment 108478 [details] Video of the Control Z working LO Writer 4.3.2.2 Win 8.1
Sorry, I didn't know that adding the attachment would post my comment right away. I could not reproduce the bug.
What operating system/LO version are you using?
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