The word character describes who you truly are morally and personally, while your reputation is what other people think of you. Not only do people have reputations, so do churches.
Congregations are usually known by how many people attend, how big or fancy the building is, how much money they raise or spend, how youthful the pastor looks, the style or size of the worship band, or how many activities go on during the week. These are the things that grab the attention of most people, but a reputation can be very different from true character.
The Apostle John sent a message from Jesus to the church in Sardis (Revelation 3:1-6). This congregation had a reputation for being alive. Theirs was a church going places, ripe with activity, making a difference in the community, and changing lives. It was a congregation people wanted to be identified with, where people could do something great and be part of something great. What everyone else thought was alive, Jesus said was actually dead (Revelation 3:1). The reputation didn’t match the character of the congregation.
The believers in Corinth thought of themselves as super-spiritual, but consider their true character. They were deeply divided (1 Cor 1:10-4:21), approved of incest and even gloated about it (1 Cor 5:1-13). The people sued each other in court (1 Cor 6:1-11), visited prostitutes (1 Cor 6:12-20), served idols (1 Cor 10:14-22), got drunk at the Lord’s Supper (1 Cor 11:17-22), and many other things! Their reputation for being super-spiritual was far removed from their character.
When Paul wrote to the church in Rome (Rom 1:8), their reputation was the same as their character: Your faith is spoken of throughout the whole world. They were genuine. Their faith was real and their faith was placed rightly in God. They probably didn’t have activities every night of the week, play the latest popular music, or think of themselves as anything great. They were, however alive and thriving in their relationships with Christ, evidenced by growing in their knowledge of God through the Word.