Which actually works, because that's exactly what you'd have to do!
Where heavy petroleum fractions and other applicable refinery streams are broken down into lower molecular weight hydrocarbons
The cat feedstock is some nasty material that looks worse than most crude oil.
It would seem feasible to introduce a small percentage of waste hydrocarbon plastics to the cat feed as it was being processed, in order to at least recover a bit of the fuel value from the plastic.
I can only imagine it is simply cheaper to continue to purchase the equal number of barrels of regular cat feed than it is to attempt to displace some of it using waste polyethylene & polypropylene which may even be possible to deliver at no material cost.
OTOH, for all I know people may be doing this already.
Of course, one should never be one's own editor as one always misses something - that is until one reads it the next day and sees one's glaring typos! But that's impractical.
It seems to me that a partial solution would be to allow small/limited edits after the normal timeout and or highlight the changes in some way. This would negate the problem of a subsequent poster's reply comment sounding ridiculous if the original post was altered too much.