IMHO we shouldn't do this, because it will lead to even more confusion. If I can't see that modification, and for me the question would be last active 6-8 weeks ago, why does it then show at the top of the list of active questions? One could take this change even further, by showing a different list of active questions for 10k users and sub-10k users, but that already gets more complicated.
Also, this denies sub-10k users the possibility to see that there's something going on with the question. Right now, if I was interested, I could still ask a 10k user in chat if they can tell me what's going on. I remember cases in Charcoal HQ where somebody 'needed' to know this for a possible spam investigation.
An alternative solution to clear the confusion would be to show a popup (e.g. underneath the 'active today' label in the widget on the top right) with a text like
The question was last active today, but you can't view the change because it was on a post that is now deleted.