Multi-Select Text box has text stating ""select up to 20 choices"" below the field. How can I get rid of this?

Well it's been ten months since you asked this question and no change. What do you think the odds are that QuickBase will prioritize this feature ahead of other more functional features? The probability is zero in my opinion and the rationale would probably include the argument that the text is not technically incorrect and that the current implementation does not break anything or disturb the normal operation.

Moreover, what do you think the product would look like if there were checkboxes turning on and off every feature users asked for? The solution is to have reasonable default behavior but the ability for users to customize point features. To implement this strategy of allowing a user to customize one-off micro features requires more access to script and HTML fragment templates. There is a long tail of features users want that simply can't be hard-coded into the product.