Thank you,

Unfortunately, the reason is that your website is hosted on wordpress.com. I really don't know if there is a way to stop caching  saving images in wordpress.com CDN system. You should contact to wordpress.com support. They may provide some code to stop caching avatars.

Robert, thank you so much. I will pursue that with Wordpress.

While I have you here, do you have any advice/code I can use to adjust the padding on the mobile version of the forums? While I don't want the posts to go all the way to the edge of the screen, the padding is a bit much as it is.

This is what I have in the Forums->Settings->Style CSS section (it may be something I messed up):

#wpforo #wpforo-wrap {
font-size: 13px; width: 100%; padding:20px 40px; margin:0px;
}
#wpforo #wpforo-wrap .wpfl-1 .wpforo-category {margin:10px 0px -1px 0px;}
#wpforo #wpforo-wrap .wpfl-1 .wpforo-forum {margin:0px 0px 2px 0px;}
#wpforo #wpforo-wrap #wpforo-menu { background-color:#777777; }
.fa-lightbulb:before {
content: "\f072";
font-weight: 600;
}

@media screen and (max-width:480px) {
#wpforo #wpforo-wrap .wpforo-post .wpf-right ul li {
margin: 2px 0px 2px 7px;
}
}

Here's a screenshot:

Try this CSS code. Add it in  Custom CSS Code textarea. Save it, delete all caches and pres Ctrl+F5 on forum front:

@media screen and (max-width:480px) {
    #wpforo #wpforo-wrap {
       padding:20px 5px;
    }
}

Then use mobile browsers private session to check. Mobile browsers do hard cache so you may not see the change. Use other devices or browsers to avoid caches on mobile.

Richard,

Have I mentioned you're my hero? 

Thank you SO much!