From the fatboy needs a rework thread...
https://discord.com/channels/549281623154229250/1480908986407452915
One problem with fatboys is pawn/grunt surround can be ineffective because the fatboy can destroy everything at its feet with no downside, as self damage is disabled for all units by default.
This reduces the effectiveness to one of thr counters to heavy units (spam) and reduces the micro requirements of the fatboy/tzar pilot. Adding self damage would require and reward skilled hold fire micro, as well as reward players who damage to get on top of the unit.
These heavy units can already damage eachother, so this change has the most impact when there is only one of these heavy units, but would have less impact if you had many, since they already do friendly fire damage if spam gets in close. As a result, it is a nerf to the most oppressive fatboy (the first one) without punishing the player who likes to make 10.
I think self damage should be enabled for everything, which is consistent with being able to damage ally units. I would bet that many players think self damage already exists.
Here is a video where @smoky ore enabled self damage. Thanks to him for testing things out.