I looked at that a bit. The Swift hashtag parsing code handles Unicode properly but the C hashtag parsing code does not, and the latter is the one that needs fixing, I believe.
Discussion
yup, we also need to get rid of the Swift parsing code because it’s extremely slow and will even completely hang the UI on large posts.
Did you try using the Time Profiler Instrument to find out specifically what was slow about it? Might be optimizable. Is this parsing being done on the main queue?