When you say there may be a long streak of high/low days…. do you mean there may be several says (presumably in a row) which all have the lowest amount and same for highest?

Yep.  Suppose someone’s looking at a savings account that only get money once every couple weeks.  There could be a lot of days with the same or low high balance.

I may be able to get really fancy and if there is a block of high/lows as described above – to only outline the block, not each cell (remove the colored borders between the cells in the block).

Now that would be pretty nifty.  :)

It might also be something that one could turn on and off, similar to the categories.