The reason is avoiding comments are used to spam.
Spammers don't write post questions, or answer questions before spamming. As consequence, they cannot write comments (since their reputation is 1), which would not cause the question to be bumped on the front page. This means only few users would notice somebody wrote a spam comment: the users who wrote the ...
Comments fill a very specific purpose which is not immediately apparent until you have a bit of experience the site. The minimal reputation requirement is a way to show you have that experience before you use that feature.
Without that experience, most incoming users would likely jump to using comments like miniature forums and chat rooms… which ...
That is how Stack Exchange works: When the question is older than X months, you keep the reputation you gained from your answer's votes, when the question is deleted. (The same is true for the question that still gives reputation to the OP even when the question is deleted and it X months old.)
That is not true for the tag score, though.
From How does "Reputation" work? (emphasis mine)
You gain reputation when:
you associate accounts of two or more Stack Exchange network sites, and at least one of those accounts already has 200 or more reputation:
+100 on each site (awarded a maximum of one time per site)
I turned up this in my search, but it was a bit tricky to find - what's the justification for the commenting reputation requirement?.
The basic reasoning seems to be as follows (taken from the linked question) - but I'm sure a mod can expand further on this :):
The justification is simple: we don't want the site to be flooded by
comments from passers-...
I do not think this will make it any better than worse (wondering what clive and other multi-thousand reputed users would say).
These units are made to avoid what you are trying to get back.
8 GB is, in my opinion looks decent than 8192 MB.