ZDoom

This is caused by [url=https://github.com/coelckers/gzdoom/blob/master/src/playsim/p_map.cpp#L5890]this code in RadiusAttack[/url]. It applies DONTHARMCLASS and DONTHARMSPECIES even when thing == bombsource, which is kinda nonsensical.
I don't think it's a good idea to just fix it now, though, since some mods might have abused this behaviour, be it on purpose or by accident. It's probably a better idea to add a flag to RadiusAttack and A_Explode to make it handle thing == bombsource correctly.

class DoomImp1 : DoomImp
{
	Default
	{
		+DONTHARMCLASS
	}

	override void PostBeginPlay()
	{
		A_Explode (500, 260, XF_NOTMISSILE | XF_HURTSOURCE, false, 180);

		Super.PostBeginPlay();
	}
}

class DoomImp2 : DoomImp
{
	Default
	{
		Species "SomeImp";

		+DONTHARMSPECIES
	}

	override void PostBeginPlay()
	{
		A_Explode (500, 260, XF_NOTMISSILE | XF_HURTSOURCE, false, 180);

		Super.PostBeginPlay();
	}
}

Here's the situation:
I have this [url=https://gitlab.com/accensi/bullet-crew/bullet-eye/-/blob/eeca164797dc5cd73c04aa53c7b15d4804590665/ZActors/Weapons/Rapid/ViperWave.zsc#L20]line right here.[/url] What this override does is it makes every poisoned enemy call A_Explode. So far so good, but some enemies have +DONTHARMSPECIES, which makes this attack do practically nothing on themselves or other nearby actors of the same species if XF_NOTMISSILE is supplied. Omitting it works as expected (by me).

Here are some actors to test with:
[code]class DoomImp1 : DoomImp
{
Default
{
+DONTHARMCLASS
}

override void PostBeginPlay()
{
A_Explode (500, 260, XF_NOTMISSILE | XF_HURTSOURCE, false, 180);

Super.PostBeginPlay();
}
}

class DoomImp2 : DoomImp
{
Default
{
Species "SomeImp";

+DONTHARMSPECIES
}

override void PostBeginPlay()
{
A_Explode (500, 260, XF_NOTMISSILE | XF_HURTSOURCE, false, 180);

Super.PostBeginPlay();
}
}[/code]

Neither of these will die when they are spawned. If you remove XF_NOTMISSILE, they will.

The reason I'm reporting this is to determine if this is a legit bug or if a foil flag could be added to A_Explode to allow explicit damaging of same-species actors.