Delta allows to sell "ICO" coins however this does not work properly.

For example, I just recorded a sell of an ICO coin (unfortunately it was only listed in Exrates, which is not a supported exchange, so I cannot “merge with tradeable coin”).

After recording the sell, it still appears in my portfolio, and with a significant market value, even when I have zero holdings, affecting my overall balance.

I think that if you have zero holdings, it should automatically disappear from the portfolio (provided you have that enabled in settings). And the market value should be zero.

I think this should be fairly easy to fix. ICO coins recorded in Delta should have the same functionality of tradeable coins, since you have the purchasing price, also the selling price (if sold), so you can properly calculate profit or loss. The only difference is that you cannot trade them in exchanges, but other than that, the functionality should be exactly the same.