Paste seems to be a problem regarding Writer and elsewhere in Libre. When copy and then trying to paste a text fragment from another source, Libre via mouse doesn’t allow pasting it (paste selection seems inactive). That’s really a catch. It is really inconvenient writing an assignment for instance to use all the time ctrl+v.
Do you mean usage of mouse middle button? This may be a matter of OS configuration (you didn’t mention its name). Middle mouse paste works on my Linux box.
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Likely tdf#136175 if on Windows.
(Offtopic: I am always surprised seeing people who find it inconvenient to use Ctrl+V instead of moving and pointing the mouse and clicking its button … but whatever…)
@mikekaganski: they may be left-handed. Ctrl+X C or B can be pressed with left hand while right hand moves the mouse. The “real catch” is being forced to alternate between keyboard and mouse.