Currently when you visit a user’s activity page as anon you can have a look at lots of info by working through the tabs (all, topics, replies, likes, solved, votes, etc) However, the /activity/reactions page gives an ‘access denied’:
I’m not sure why this info in particular is restricted when all the other tabs are fine? I think this should either be viewable or the reaction tab hidden for anon to avoid the issue.
(I think this has been mentioned previously but hasn’t yet got a dedicated topic)
Related topics is always my friend 
I think this topic is about the same issue If a user has not reacted to any topic or message, then this page (/activity/reactions) gives an error (though mixed in with a suggestion to also improve the text when there are no reactions to view)
And the one I was originally thinking of - Reactions page glitches view when attempting to fetch more posts where no more posts exist - #6 by JammyDodger