I don't really know what there is here worth debating other than the actual text. The text is the only thing that objective conclusions can be made on. Everything else is conjecture or personal preference.
We do have to remember that in 5e, personal preference (aka DM ruling) is the law of the land. 5e is not 3e, it is not built on legal grade wording that can in all cases be objectively deciphered. 5e is intended in its core to provide guidance and rely on DM interpretation. This also means that 5e is NOT written with the same amount of stringency that is in 3e. The simple truth is, some sentences that people meticulously try to pick apart.....are simply not written well.
So does that mean debate is pointless? No...but I think its focused in the wrong area. We are trying to suss out Vecna's exact ability from text analysis, when I think its more productive to look at other sources:
- CR: Its 26, what interpretation of Vecna's counterspell ability is more in line with a CR 26 monster?
- Flavor text: We have been given various descriptions of Vecna. What interpretation is more in line with the flavor?
- Niche Protection: We know that Sorc's have been given some measure of "counterspell immunity" using subtle spell, at least according to Sage rulings in the past. Does it then make sense to continue that tradition on "counterspell like" abilities. Aka is it better to enforce a protection for sorcs, or more important to give Vecna (being a notable high level BBEG in our common dnd lore) some special niche protection in this case?
Now for me, those questions generally lead to the conclusion that "dread counterspell should thwart subtle spell. Vecna is statted as a highly anti-spellcaster monster. He is also flavorwise noted as the "ultimate spellcaster"....yet doesn't even have 9th level spells. To me one of the ways to maintain that flavor without of lot of high level spells is with the ability to stop all enemy spellcasting around him. Against Vecna...your power means nothing. I also feel like this is more in line with a CR 26 ability, because otherwise casters with 9th level spells (which are obtained as early as 17th level) have various ways to beat Vecna down.
On the other hand, a sorceror sending out a regular chill touch to block regeneration (which Vecna will want to counterspell because its potency) and then follow up with a quickened spell (that cannot be dread counterspelled because a reaction has already been taken on that turn).....seems to do the same fundamental thing, getting past Vecna's counterspell. So
sorc's can already do it, is it fair that a sorc that took quicken spell can do it, but subtle spell can't? You could argue that Vecna has agency against quicken spell, but has no agency against subtle...but at the end of the day a properly built sorc has ways to get past Vecna's ability that no other caster has....so does it really matter which way (quicken or subtle) you go about doing it?
