No. There is a special version of the neutral assay, with prolonged lysis at elevated temperature with or without proteinase K, which does apparently only detect double strand breaks (Olive et al. , Cancer Res 51, 4671-6). It is not clear how this works, but the digestion conditions probably destroy the nuclear matrix and loop attachments. Perhaps double stranded fragments then migrate in a conventional way.
It is possible to produce tails without breaks (single or double) in neutral comets. Relaxation of torsional tension with the intercalating dye ethidium bromide gave tails while higher concentrations of ethidium bromide caused the tails to diminish as positive supercoils built up; no such effect was seen in alkaline comets (Belyaev et al. (1999), BBA 1428, 348-356).
"FAQ by Andrew Collins, Gunnar Brunborg and Jonas Nygren, 2006, NewGeneris FP7-project"