In chapter 43, JA tells that:

The next day produced little or no alteration in the state of the patient; she certainly was not better, and except that there was no amendment, did not appear worse. Their party was now farther reduced; for Mr. Palmer, though very unwilling to go, as well from real humanity and good-nature, as from a dislike of appearing to be frightened away by his wife, was persuaded at last by Colonel Brandon to perform his promise of following her; and while he was preparing to go, Colonel Brandon himself, with a much greater exertion, began to talk of going likewise.

I don't think that JA intends "real humanity and good-nature" as being ironic; only that they were not the only reasons he stayed.

Col. Brandon also talks about leaving, but Mrs. Jennings persuades him to stay; Mr. Palmer agrees with this:

Mrs. Jennings's entreaty was warmly seconded by Mr. Palmer, who seemed to feel a relief to himself, in leaving behind him a person so well able to assist or advise Miss Dashwood in any emergence.

These are Elinor's opinions about Mr. Palmer:

Elinor had seen so little of Mr. Palmer, and in that little had seen so much variety in his address to her sister and herself, that she knew not what to expect to find him in his own family. She found him, however, perfectly the gentleman in his behaviour to all his visitors, and only occasionally rude to his wife and her mother; she found him very capable of being a pleasant companion, and only prevented from being so always, by too great an aptitude to fancy himself as much superior to people in general, as he must feel himself to be to Mrs. Jennings and Charlotte. For the rest of his character and habits, they were marked, as far as Elinor could perceive, with no traits at all unusual in his sex and time of life. He was nice in his eating, uncertain in his hours; fond of his child, though affecting to slight it; and idled away the mornings at billiards, which ought to have been devoted to business. She liked him, however, upon the whole much better than she had expected, and in her heart was not sorry that she could like him no more; not sorry to be driven by the observation of his Epicurism, his selfishness, and his conceit, to rest with complacency on the remembrance of Edward's generous temper, simple taste, and diffident feelings. (Ch. 42)

So Elinor has in general a good opinion of Mr. Palmer; although she recognizes his defects and compares them with Edward's virtues.