Can a seller be sued just for entertaining a better offer during exclusivity?

It depends entirely on how broadly the exclusivity or no-shop clause was drafted, since "entertaining" an offer and "accepting" one aren't always treated the same way. Some clauses are narrow, prohibiting only soliciting, negotiating with, or signing an agreement with another buyer. Others are drafted much more broadly, prohibiting the seller from even receiving, discussing, or considering an unsolicited approach at all during the exclusivity period.

The trap is assuming that because you didn't actively pursue another offer, or didn't accept it, you're automatically in the clear. If your clause is broadly worded, simply engaging with an unsolicited approach — replying to it, taking a meeting, or sharing basic information — can already fall within what you promised not to do, regardless of whether anything came of it.

Whether a specific interaction crosses the line depends on the exact wording of your clause, not on your intentions or how far things actually progressed. Before responding to an unexpected better offer while under exclusivity, have a Treadstone business lawyer confirm what your specific clause actually restricts, since the safer assumption is that it may cover more than you think.