Today Italy prices its new 20y benchmark maturing in Mar41. Fair values are around a yield of 1.78/80%. However in Italy it is important to compare bonds with similar coupons. If you wanna know why, here is a thread!

Theoretically, there should not be any difference in the yield of two bonds with different coupons. See these 3y bonds: the higher the coupon, the higher the bond price - yield stands the same (2%).

In fact, the lower the coupon, the higher the duration of the bond (i.e. it takes more time to recover your investment). Using simple Macaulay duration in previous example:
1%cpn=2.96y
2%cpn=2.94y
3%cpn=2.91y
More duration, more risk! So why market favours low coupon bonds?

Why? Low coupon bonds in Italy use to trade at lower yields (+price). As yields have fallen in the last 20y, low-coupon bonds use to be newer references. Also, all bonds sold after Jan13 need to have CACs (easier to restructure if default) and have smaller loss given default

Smaller loss given default means; imagine there is a default and investors recover 30% of the nominal value of the debt. In the example above, depending on coupon you would recover:
1%cpn-30/97=30.9%
2%cpn-30/100=30%
3%cpn-30/102.8=29.2%
(+)Cpn=(-)recovery

These forces are such, that if you take the yield of the high-coupon bond vs the interpolated low-coupon neighbours on the curve, the spread does the same than the BTP-Bund spread. REMIND, coupons in Italy matter, and follow mesures of credit Risk.