In addition, the way attachments are handled now, is that anyone hotlinking to a post attachment will go through the UBB.thread security check. Previously, some attachments were directly linking to the files directly on your forum server. A few versions back, this security was corrected so that only users/user groups with access were able to view those files.
A side effect of that is that the end user viewing the image will now get added to your Whos Online list, since they are being checked for access.
Prior, it would only appear in your server logs, not UBB.threads logs. As for why your post-view count is going up, may be related to a bot getting stuck trying to index your site, or attack it. or even a malicious user who had setup their browser/system to auto-refresh your page every "XX seconds", with the intent of purposely slowing down your forums.
Scripts such as described are easy to find. In fact, I've used them in the past for their intended use... To watch a sale-page for if an item is marked as back-in stock/available. [example/off-topic] Buying a Google Nexus (now Pixel) on release day? lol. Refresh that page every few minutes to see if another wave has opened up, allowing you to jump in that short window of time where you can pre-order it.
