凡哥历来低调、谦逊，向凡哥学习！遵从凡哥的意见，我也谈谈这个问题。我把commit 表示“承诺”的用法，列为三组：

A 组：
He committed himself to supporting his brother's children.
He committed himself to support his brother's children. （美国英语）

B 组：

He was committed to supporting his brother's children.
He was committed to support his brother's children.

（去掉反身代词，变为被动式，但意思并无被动，同A组）

C 组：

为求简练，省掉A 组的himself，或者人们觉得， B 组用was 啰嗦，直接也省掉。得到：
He committed to supporting his brother's children.
He committed to support his brother's children.

最后一句，commit 的用法跟网友的句子一样。只是，committing 用了动名词，是因为它做了介词 including 的宾语。

新闻语言、网络语言、包括口语在内的非正式语言，无不都在简化表达方式。
当今社会是信息时代，时间是最宝贵的。因之，语言交际趋向简洁明了。“简练”是语言的精髓。现如今，新闻语言和网络语言，占据着人类交际语言的半壁江山。由各种多媒体承载的语言素材，纷沓而至，应接不暇。语法研究也要与时俱进，不要一味地从故纸堆里，包括数十年前出版的英语语法书、英文词典、英文报刊，以及古典文学作品中，寻找一成不变的理论根据，否则就会落伍的。

我只认可

1.  The president is personally committed to this legislation. 此时committed为形容词，to为介词，接名词或动名词doing，不认可接to do，句子来源牛津字典

2.  Making an application does not commit you to anything.  搭配关系commit somebody/yourself to something，此时commit的宾语为相关人物，to为介词，接名词或动名词doing，不认可接to do。句子来源牛津字典

3.  Twenty port authorities in Asia, Europe, the Middle East and North America signed a declaration committing to stay open amid the coronavirus pandemic. 来自bloomberg英文网站，

此时搭配为commit to do，表示答应做什么，不定式to do为commit的宾语。我查了牛津字典，没有例出这种搭配，剑桥字典也没有，不知道为什么，但google一下，例句相当多。从原理上讲，commit不应该排斥直接加不定式的搭配。

       我没有查到 commit 后面直接接动词不定式的例句。

       现代英语（尤其是美国英语）中，commit sb（或 oneself）to 后接动词原形的用法已司空见惯，往往可以和 v-ing 形式互相换用。例如：He has committed himself to support（或 supporting）them. 他答应负担他们生活费用。（摘自《薄冰英语惯用法词典》p.166）

       commit oneself = be committed ... (2) 约定，承诺（做...）(to, to do) : I didn't commit myself to attend [or attending] the meeting.  我没有答应出席那个会议。/ He was committed to follow my advice. 他答应听从我的忠告。（摘自《英汉多功能词典》新编升级版p.322）

       I have committed myself to go (going). （摘自张道真《现代英语用法词典》修订版p.255）