This question is a StackExchange Frequently Asked Question and the answer is here (which I copy/paste below). It's a trade-off: a lower threshold implies more irrelevant chit-chat in comments (sometimes at the cost of missing out on useful comments).
Note: the 50 reputation doesn't apply to your own questions.
It's a StackExchange-wide threshold, so we wouldn't be able to change it for this site. Removing the threshold was proposed here and subsequently declined.
Why does this limit exist?
We realize that new users may have valuable comments, and that we may
lose some of those contributions by requiring 50 reputation points to
unlock the feature.
However, history and experience have shown that the downsides of
allowing everyone to comment are far greater than a few useful
There are big problems with spam. Automated filters cannot catch all of it.
Even among the real comments, most would either say "I have the same problem" or "I agree". Such comments do not add any value, and have to
be manually removed.
Comments are very painful to moderate. Stack Exchange sites have a process of community moderation (voting, flagging, review queues) that
works great for questions and answers, but not so much for comments.
Comments cannot be downvoted or closevoted, nor searched (nor do we
Comments are second class citizens on the Stack Exchange network, not designed to hold information for all eternity. They may get
cleaned up at any time. Generally, truly important information
should be incorporated into an answer of its own anyway.
Providing good answers will get you 50 rep points in no time.
Alternatively, you can suggest edits that improve existing
questions and answers. Each of those will gain you 2 reputation
But I want to contribute now. What should I do instead?
Can I put my comment in an answer?
Asking and answering, the core actions on the Stack Exchange network
of sites, are open to all users regardless of reputation.
However, this is not meant as a workaround to the comments barrier.
Comments posted as an answer are subject to removal.
To make requests for clarification, or mere responses to other
answers, you need to wait until you have the comment privilege.
How do I write a good answer?
If you are sure you can provide a real answer, then you are of
course welcome to go ahead, but make sure it's a full, valid answer
to the question. If you saw something wrong with an existing
answer, do mention it and its flaws, but make sure you provide an
alternative solution that can stand on its own. Do not just copy
and paste your original comment into the "answer" field.
But I can't write a good answer without more information!
Answers don't have to be exhaustive or infallible, they just need to
try to answer the question. It's perfectly fine to post an answer saying, for example, "I'm not sure what the cause of your problem is,
but if it's X, you can solve it by doing Y. If that doesn't help,
try Z and let me know what it says." Also, if further information
does become available, you can edit your answer later to make it more
precise. This is a good habit to get into even if you can
Welcome to the community, and good luck!