This is more of a global Stack Exchange policy than one specific to UserExperience.Stackexchange.com, and has been discussed in the past over on the main meta.stackexchange.com site
But in summary; The purpose of Stack Exchange is a question and answer site. Comments are secondary and are not essential to the use of the site. You can ask questions and provide answers with no reputational requirements.
The reason for having a restriction on when you can comment is that this provides enough of a buffer for new users to get an understanding of how the sites operate and what sort of content is and isn't appropriate. If anyone could comment then the site would be full of "+1 Great answer!" comments against posts. Comments are for requesting clarification on posts, pointing out errors and suggesting improvements. Not just for general discussion (this isn't a social network). It also helps prevent spam (which is quite a problem across Stack Exchange).
You can comment on your own posts though, to reply to point raised in comments about your question/answer though.
Looking over you answers; two of them could easily be reworded into actual answers:
This one: When customizing your iWatch face the time changes to 10:09 is a bit on the speculative side though, so would likely be (and has been) challenged. But you can improve this by providing some research and elaborating.
This one: What is the best mobile number authorization strategy? without the commentary aspects would equally work as an answer, albeit requiring some fleshing out.
One I had to delete because it just stated you didn't know what an acronym meant (and if left as a comment that too would likely have been removed over time because it's not really adding anything to the question).