ZDoom

The discussion at the time basically stopped at "when should we interpolate movements implicitely" here.
Looking back at it, here's what I think should be done based on one of Xaser's posts:

• Bobbing: Interpolated period. Why would you want to disable interpolation for such a thing honestly?
• Raise/Lower: Interpolated by default. Can be disabled with an A_Raise/A_Lower parameter.
• A_WeaponOffset: Interpolated by default. Can be disabled with a parameter as well. IIRC this function came around at the same time I did the overlay stuff so people using it should be aware of the interpolation which is why I think it should be on by default.
• "Offset" keyword: I'll have to agree with Xaser here and make it off by default as old mods used (and could only use that) it without the interpolation in mind which gave rise to some reported issues HOWEVER I would like the possibility to turn it back on with a CVAR as I think it looks great regardless with some old weapons that made proper use of offset animations.
• Finally, add a level-based CVAR with the following options: never interpolate, default behavior and default with enforced interpolation for the offset keyword on top of that for people like me.

This should make everyone happy: every issues should be fixed, modders have access to the interpolation using the proposed parameters and users can set it up to their liking.

Agreed mostly. I think, though, 'offset' should be extended then by an optional third boolean parameter that can explicitly enable interpolation. With that the Hexen weapons could be fixed and everything was perfect.

Agreed and agreed. The "never/default/always" setting is the best way to handle it.

And hopefully can fix a certain bug that's been bothering me for a while.

This is probably implicit, but agreed with Leonard2 and Graf. That oughta square it away for everyone.