That's not to say lignite is in any way "good", it's still a horribly inefficient way of getting energy. But peat stores large amounts of methane and carbon which gets released when drying it. Mining lignite coal also release some of that, but in much smaller amounts.
A quick estimation about the environmental impacts (with data for Germany only) shows peat is at least 5-20 times worse in terms of surface destruction - I have no idea how to compare the ecological impact of removing a biotope vs. moving a town.
Lignite:
- thickness of a lignite bed 11-35m [0]
- surface destruction per metric ton: 220-700 cm² [0]
Peat:
- thickness of a peat layer 1,5-2m [0])
- surface destruction per metric ton [1]:
-- at least 3,850-5,130 cm² (using the same density for coal and peat)
-- 6,000-8,000 cm² (moist peat, 0.8g/cm³ [2])
-- 10,000-13,300 cm² (dried peat, 0.4 g/cm³ [2], considering the higher calorific value for peat [4])
-- at worst 12,000-16,000 cm² (dried peat, 0.4 g/cm³ [2])
[4] The gross calorific value for peat is 5-20 % higher than for lignite [2]-[3]; though I guess that does not exclude the energy needed for drying the peat.
That's not to say lignite is in any way "good", it's still a horribly inefficient way of getting energy. But peat stores large amounts of methane and carbon which gets released when drying it. Mining lignite coal also release some of that, but in much smaller amounts.