Nobody is saying you are putting your baby at risk because of the stairs. Nobody is having a go at you.
What people are posting here is that potential buyers will be aware of the hanging hazard and will keep scrolling when they see your stairs because there are other houses on the market that do not have this hazard that would have to be taken care of immediately.
The stairs are absolutely not an issue and DDs head couldn't fit through them. Plus who on earth allows a baby/toddler to climb stairs unsupervised?
Lots of babies slip off for the three seconds it takes to get over a gate and onto a stairs unsupervised. Just because it hasn't happened to you doesn't mean it has never happened. Lots of potential buyers can't see themselves watching a baby or small climbing toddler like a hawk to make sure nothing horrible happens with an open stairs. A climbing toddler could get over a gate with little effort. Many people have toddlers who are little divils, to use an Irish phrase.
Your view of the stairs as the owner of the house is not necessarily going to be the view of potential buyers who are also parents of babies or toddlers. Your main market is young families so you should be willing to take concerns about the safety of the stairs on board. If a baby or toddler slipped their legs and torso between the steps there could be a tragedy.
Likewise, people's concerns about the usable space/third bedroom should not be met with legalistic arguments on your part. What you see here is a representative sample of opinion about the safety of that space and I think you should take it seriously. If people have concerns about safety they are going to jog on or put in a lower offer than you are willing to accept.