@Afrodude When I say "it doesn't work here", I mean that the counter shows, but as zero instead of the correct solved counter when I remove the {if} statement.
Think about it: in the original logic, if $comment->author_solved_count is different from zero, then the counter is shown. The only occasion that the HTML tag/counter wouldn't be shown is if $comment->author_solved_count = 0.
If I remove the if statement, the counter is displayed as 0, however, this user's solved counter isn't zero (it is 53)... As I said, the source code is forcing the counter to be zero even when it isn't when the post is in a forum that has the solved option disabled.
I made a very simple test: I enabled "Enable Solved?" for that forum and the counter was displayed (as 53, not zero). If I disable this option, the counter is displayed as 0 (with the {if} tag removed).