I think this should go into the markdown reference here https://www.girlswithmuscle.com/comments/mark...
If it’s to an image in the gallery, then it’s preferable to link to the image’s page, otherwise you are making people do work to find the page it’s associated with.
Just for clarity, the instructions given by RoseFeni are only for offsite images. At the same time some sites will block hotlinking of images from another site’s page.
You can link to a site image by copying the direct image URL and using the forum’s image tag. Most forums use this format:
[img]exampledotcome/image.jpg[/img]
If images don’t show, you can use a normal link like this:
exampledotcome/image.jpg
Make sure the link ends with .jpg, .png, or .gif.
This is completely incorrect, [img] does nothing.
It's very simple. All you need to do is copy the link to the image page and paste it into the text box.
You don't need to link it with the link button. All you will end up with is a link that just reads "link text." If you do it the way I described above, your comment will automatically have a thumbnail preview of each image link you pasted once you hit the "Post comment" button.