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May 19, 2021 at 11:53 comment added Zach Teitler I was thinking of a hyperplane tangent along a line in $X$.
May 19, 2021 at 6:59 comment added Leo D Thanks @abx for your beautiful example. The idea of considering the Veronese makes everything so concrete.
May 19, 2021 at 6:54 comment added Leo D @ZachTeitler if I didn't meantion that X is smooth, there you are right there are a lot of counter examples---those who contain linear components. But if I require smoothness, then maybe there is only one exceptional, the hyperplane.
May 19, 2021 at 6:06 comment added abx I am not sure I understand the question : as the OP mentions, there are no such examples with hypersurfaces. All you need is a hyperplane section with a singular locus of dimension $>0$ —which can of course be a linear subspace.
May 19, 2021 at 5:23 comment added Zach Teitler Are there additional examples whenever the variety contains a linear subspace? Those are plentiful including for hypersurfaces.
May 19, 2021 at 4:46 history answered abx CC BY-SA 4.0