Why does Paul speak positively about boasting when he refers to "crown of boasting"?

Paul further describes the crown as the crown in which we will glory. More literally, the crown is a crown of boasting (Greek: στέφανος καυχήσεως/stephanos kauchēseōs; see also ESV). Given the very negative statements Paul makes elsewhere about boasting (Romans 3:27; 1 Corinthians 1:26–31; 2 Corinthians 11:16–18), it seems strange that he should express such freedom to boast here. However, the boasting of which Paul speaks is not an expression of arrogant pride, but rather a statement of great confidence that the thing boasted in is truly exceptional.¹ Paul was confident in the Thessalonian believers and he took delight in celebrating their conversion and ongoing faithfulness to the Lord Jesus. Although it is not explicitly stated here, Paul’s confidence was essentially a confidence in the work that God had done in the Thessalonians’ lives, and this work attested to the genuineness and success of his own ministry (see Romans 15:18–19; 1 Corinthians 15:10; 2 Corinthians 11:16–18). For this reason, the perseverance of the Thessalonian Christians enabled Paul to look forward to the day of Christ’s return with confidence and assurance: the grace of God evident in their lives meant that he could look forward to that day without fear of being put to shame, or of his work proving to be worthless.