Which may now be obsolete. Over the last year firefox has implemented some amazing flexbox layout computation improvements that make appending to a flexbox with many elements (>5k) stay fast. It only re-computes the changed ones.
Of course you need to do some profiling to check that you don't accidentally deviate from the happy path by introducing changes that touch all elements.
I noticed when trying to screenshot a Twitter thread in Firefox that twitter does this, on the mobile site at least.
The question is, is this the best use of your time? Are you willing to invest more time in it when you give it to the user? Because the user will do something you haven't thought of, they will break it, and you will need to fix it.
Although to be "fair", that's probably largely intentional crippling of the site to push users towards their app.