Children listed on links tab are displayed with strikethrough font
Accepted answer
strike through is for resolved (work items in closed state) work items.. verify the state of the work items and if the current state is one among the states mapped to Closed OSLC state group, you could expect the strike through.
Open PA in Eclipse Client > Process Configuration > Project Configuration > Configuration Data > Work Items > Workflows > State Groups > Look at the value for "Category" and / or "OSLC Groups" of the State
Open PA in Eclipse Client > Process Configuration > Project Configuration > Configuration Data > Work Items > Workflows > State Groups > Look at the value for "Category" and / or "OSLC Groups" of the State