This week's book giveaway is in the Kotlin forum. We're giving away four copies of Kotlin for Android App Development and have Peter Sommerhoff on-line! See this thread for details.
You should not be using the ternary operator for this, but using the <c:if> tag. Why not use what's clearest and most appropriate? Embedding HTML inside strings is a poor practice, and ternary operator is intended as a simple expression switch, not as a replacement for a conditional statement.
And, no you cannot embed an EL expression inside another. The ${} delimiters enclose the entire EL expression and there is no need nor allowance for nesting them.