You can make use of the $db->insert_query_multiple method in your installation to reduce the number of queries. It takes one parameter, a multidimensional array with the data.

An excellent plugin and well needed on my forum so I can see who has read announcements.

Two suggestions are:

Permissions on who can see the people who viewed the thread. In my circumstance, I feel like it is better only staff members are able to see this information. Of course if there is another way around it then great however I would love an ability to hide this by group rather than guest/logged in only.

Even if it was a separate module like in the old 1.6 "Who view this thread" plugin, being able to display dates in a friendly "Today" "Yesterday" and so on would be fantastic. See this screenshot for an example: https://i.imgur.com/oMWWw9w.png - better yet the option to display the time by the side of the name rather than hover.

Last one, the ability to activate this within certain forums only? For example in my use, this is only useful for announcements, the staff area and a few other areas.

I know it's a lot to ask but something to do if you get bored :P

I would love to hear your thoughts, thanks!

After update I cannot see who browsed a thread... + where to set show last visit instead of first visit?

There is extra space before the comma after every username