In an answer I just posted, it seems that stack.imgur.com is not resizing the images when the letters t or m are added to the filename. As an example, here's bUxeut.jpg and bUxeum.jpg:
You may confirm that the URL syntax is correct by editing this question or opening the above images individually. Currently, these display for me at the same size in the preview of this question. Past questions that I've used these image sizes in remain unaltered.
It's not ignoring all of the possible parameters, since image bUxeus.jpg and bUxeub.jpg display properly resized:
I've changed the thumbnails to the large square size (b) in the answer in question. But I greatly prefer to include the t or m sizes in my answers, as they fit very nicely between paragraphs, with two side-by-side images fitting on one line without being cropped into squares. So if there's a reason why my images aren't resizing to those sizes, or a work-around that could fix this, I'd like to know about it.