when I see an answer where I'd like to post a comment for some clarification on specific parts
I don't have any questions to ask
These two statements don't fit together. If you want to comment on an answer to ask some follow-up questions, then you have a question! It's perfectly OK to ask a question that links to another question or answer for its background. "I read this answer but didn't understand this aspect. What's going on there?" can be a good question. Better yet, asking it as a question means that everyone will see it and can try to answer - not just the author of the original answer. Maybe the original answer was vague on a couple of points because it's outside the author's area of expertise, or they just don't know how to explain it well. Maybe it was brief because an explanation that a newbie would understand is too long to fit in an answer where it's not the main point.
The thing about new users not being able to make comments is a bit of a nuisance, but the original intent was for exactly this reason: so that new users who don't realise their comment should be a question or answer, won't post comments and lose out. New users often think that posting a question is somehow expensive or there's some kind of minimum size for a question, but questions can be as small or straightforward as you like.
One last side point is that you don't need to know everything to answer. You might read some answers by high-rep users and assume they're just answering from experience, but I've posted a lot of answers where I didn't know anything about it before the question was posted. I saw the question, was intrigued, and researched it myself, finding out enough information on my own to post a good answer. Experience isn't the main variable in how good your answers can be: it's the willingness to research and put effort into writing a complete answer.