One of the major reasons it's controversial is that it has been used as a distraction and a false promise. I.e. arguments of the form "we can continue to burn fossil fuels, because some magic future CCS technology will fix everything" are very common.
Because the problem is emissions, not who creates those emissions.
What I'm saying is that if coal does so much sequestration that it in effect has negative emissions, this is actually better than solar which has a little emissions. This is because we care about emissions.
I'll make an analogy. Let's say we have two companies that output poison in their process. Company A produces 10000 units and company B produces 5 units. Company A shifts and now produces -10 units of poison and company B doesn't change. Initially company B is better but after the change company A is better because really all we care is about the poison being produced and not actually what the companies do. Because at the end of the day, our goal is less poison. That's the number that matters.
I think this is something a lot of people miss and I'm not sure why sequestration as a whole is a controversial subject (well I don't think planting more trees is _that_ controversial, though there are nuances people aren't usually aware of). We don't just need to be carbon neutral, we need to be negative. Plus there are many industries that we have no neutral method, such as concrete and steel production. Most people think if we solve energy and transportation we solve the problem instead of only solving 60% of the problem.
The other important factor here is that emissions are the problem. If coal plants sequester 110% of their emissions, there's no problem (well... in terms of CO2eq). The fact that this is a controversial subject is odd to me because it seems like the fastest way to get carbon negative. Sequester coal and natural gas plants until we can switch to a fully green (or green + nuclear, depending on your country's/region's constraints) system.
But if we talk about energy + transportation only being 60% of the issue (and US + Europe only being 30% of global emissions) it becomes much more important to talk about getting to NEGATIVE emissions, not zero (plus this helps with the 40 year lag of CO2 and temperature). And for those saying that other countries should take up their share 1) do you want to make that bet? You've all worked on team projects. We can't force them. 2) How do you ask a developing country to choose between hospitals and green energy? They don't have enough for both and one clearly has a shorter return on investment in number of human lives saved. (We can pick on China though, they're rich enough that they don't have to choose, but US and Europe need to be picked on as well).