Correcting an under pitch

Can a "yeast expert" take a look at the attached thread... really just the first 6 posts?

https://www.homebrewtalk.com/f39/big-beer-without-starter-225539/

I'm curious if simply pitching additional yeast a couple of days after primary fermentation would work.

I don't THINK it would. I THINK the 'damage' would already be done by the stressed yeast in that time frame and I don't think simply repitching another, more attenuative yeast over the top would fix the off flavors. It might dry it out a little more and correct a bit of the sweet problem but I still think the under pitching will cause issues that can't be fixed.

... but I'm not sure and curious to get someone's opinion who's pretty knowledible about da yeasties

I'm certainly no expert, but additional yeast should not hurt anything, yet it may not help anything either. But you're not really sure there is "anything" that needs fixing at this point, right?

You kind of set yourself up for problems and made it difficult on yourself by tossing in way too little yeast in this heavy brew.

Generally.... the longer you let it ferment, the higher the ABV will get, and the more difficult it will become to get some fresh yeast established.

This will turn into beer for sure, but not likely to hit it's potential flavor and attenuation.

OP - You are correct, adding a more attenuative yeast will help with the last few points of FG, but won't get rid of the problems caused by the first few day.

I wasn't the OP in the other thread... Just curious on what others' opinions were for a bit of an academic sense. I had a few thoughts on the OP's situation but wasn't sure if I was right. Just looking for a few more thoughts or a discussion.