The normal scoring of points for destroying/killing valid targets during the player character's life is reversed if done after player dies.
For example, if you launch a guided missile at an enemy AFV just before it kills you and that missile destroys the vehicle and its crew right after your death, then the corresponding amount of points would be deducted from your score as if it was a TK action.
Create a server with one friend, join the opposite teams, meet on the map and kill each other at the same time by, say, throwing grenades at each other's feet. Check the scoreboard for result.
This issue is true for and has traveled all the way from ARMA 2. Disregard completely if this is actually a feature intentionally coded by BIS to punish/discourage suicide-kills.
Well, if BIS does acknowledge that this behavior is by design then this is definitely a non-issue and our moderators can close the ticket.
Here is something else I noticed that might be related to this issue.
When mission parameters permit the use of vehicles/aircraft from other factions, dying inside as a driver/pilot results in rightfully deducted points for losing the unit. However, conversely, if you destroy that same captured vehicle/aircraft while it's not manned then the game awards you points.
Rather than a bug, this could be a mere logical hole in design of the scoring system. Just thought it might be related to the reported issue if, as TakeHomeTheCup suggested, the problem in question is actually a feature.