There is no rule against commenting more than 3 times in a thread. Sorry if anyone has gotten this impression.
However, among the 10 "Recent Comments" visible in the sidebar at right, usually no more than 2, rarely 3, and never 4, should be yours. This is meant to ensure no one person dominates a thread; it gives others a chance to respond to others' responses. One-line comments that quickly correct an error may be common-sensically excepted from this rule.
You need not refrain from commenting, just wait a bit.
Three wishes for improvement (don't know how easily done on Typepad, if at all)
1) In addition to feeds available now, an RSS or Atom feed that includes all posts and all comments to them
2) disable comment pagination
3) ability to edit comments for a short while after publishing them