I created an image crediting snippet to use in blog posts that inserts links at the bottom of posts. The block of front matter looks like this:

image_credit:
- creator: "Link 1"
  url: https://www.link1url.com
- creator: "Link 2"
  url: https://www.link2url.com/
What I was trying to do is like this, to insert a list of formatted links to those references:
{% if page.image_credit %}
    Image credits:
    {% for image in page.image_credit %}
    <a href="{{ image.url }}" title="{{ image.creator }}">{{ image.creator }}</a>
    {% endfor %}
{% endif %}
What I’m trying to achieve is to insert a comma or separator character in between the items in the loop, but not after the final item… to somehow exempt the last item. Is there a way to stick an if inside of this loop to check if the item is last and do something different?
              
Indeed there is a way. There are methods available as forloop.first, forloop.last and forloop.index to tell you where you are in the loop. Note that gere forloop is that literal name.
I came across this before and found an example now. So now add this between you text and endfor.
{% if forloop.last %}{% else %},{% endif %}
Copied from https://vsoch.github.io/2019/jekyll-lists/ You make it even shorter by taking out the else and using if not true logic.
See also this looping tutorial which a .first and .last section https://learn.cloudcannon.com/jekyll/looping-in-liquid/
And this cheatsheet https://learn.cloudcannon.com/jekyll-cheat-sheet/
              
Great!
Also I happened to come across this yesterday so wanted to add an equivalent to the above - since unless is a great way Ruby/Jekyll to negate an if condition.
{% unless forloop.last %},{% endif %}