indentation.

what is the advantage of moving this code to Column? I don't think the code is more compact now because of this change and you also need to implement the function in AbstractSimpleFilter.

if we don't need this function now, let's remove it. We can add it once we really need it.

no brackets here.

no brackets here.

doesn't have any affect. Can be also removed I guess.

no brackets for one-liners.

i18n("The column %1 is not available anymore. It will be automatically used once it is created again", m_curve->xColumnPath())

Because I need it two times.

? which brackets?

move this comment inside the function definition. This is the comment for the handling of columns only and not for the whole function which does a bit more.

in this for loop we call several set-functions which will produce a new entry on the undo/redo-stack. Do we want to have these entries if we change the name of a column? I'd say no. Le's work with curve->setUndoAware(false);
curve->set*Column(column);
curve->setUndoAware(true);

same here. Let's use setUndoAware(false) prior to setting the columns.

can be removed.

wouldn't it be easier here to provide the column and the column path directly to this function like

checkCurveAvailability(cbXColumn,  curve->xColumn(), curve->xColumnPath());

With this you'd avoid this cumbersome if-else logic in XYCurveDock::checkCurveAvailability().