I can’t read, removing most of my post as I mis-read the discussion 
That said, I am curious:
For the dual line titles, why show both to the user it has been translated for? For me, if I was browsing a foreign language forum just having the translation for me would be good.
If the topic titles were being translated, I think caching would be a must - though I am sure caching opens a whole other can of worms of where to store the data.