Posts can be edited (often by users other than the post's original author) for numerous reasons. Each SE site will have its own culture and policy, hopefully described on the site's Meta, as this post aims to do for Matter Modeling.
Meta.SE has a plethora of discussion about the topic, going all the way back to 2008 (the year StackOverflow was launched), so for various of the Meta.SE discussions I found, I will summarize anything I picked-up during my readings, and/or anything I thought would be useful to extract and/or write here.
Q: How to avoid Edit-Wars? (2010, 277 views)
- Posts on SE carry a Creative Commons license which is explained in the FAQ, so writing a post on any SE site carries many implications. It may be a good idea to familiarize yourself with these before getting upset when something that you don't like happens. Ways to avoid edit wars include: explaining your edits (e.g. in comments or in the edit summary), walking away, flagging for diamond mod attention if a rollback is problematic.
Q: Can the OP of a locked answer still edit it? (2016, 69 views)
- No, except if OP is a diamond mod. In fact sometimes the reason for locking the post is to stop the OP from rolling back useful edits or vandalizing their own post (this happens when people write an answer and then don't want it seen anymore, and when the OP doesn't understand the fact that SE posts automatically carry the Creative Commons license: you give up a lot of rights when you make the decision to post on SE).
Q: Does the OP have the right to undo edits? (2015, 119 views)
- Not if the editor improves the formatting of the post, retags the post properly, or makes the post conform better with the site's policies/standards. OP needs to understand that the creative commons license and SE policies apply to all posts, whether the author likes it or not, and therefore the OP no longer "owns" the post even if they disagree with what the community collectively agrees to do to it. Some edits might not be appropriate, and when this happens the OP can flag their own post for moderator attention.
Q: Who has the final authority in an edit war? OP or a moderator? (2017, 443 views)
- The answer is: diamond moderator since they can lock posts and OPs that are not diamond moderators, cannot. OP can try to convince diamond mods to change their mind if OP wants to try that.
Q: What is the etiquette for modifying posts? (2008, 9k views)
- Copy-editing is acceptable. Improving spelling, grammar, and/or formatting, is acceptable. Edits that change the meaning of the post are less accepted. I'll personally add that this discussion took place in 2008, and now 14 years later, my experience on SE tells me that the part about copy-editing is still true, but edits that change the meaning of the post do sometimes happen and get accepted by the community (in the interest of trying to avoid unnecessarily many conflicts, I'd recommend not trying to do this unless you have a lot of experience).
Q: How to deal with cosmetic edits to my question that I disagree with? (2014, 198 views)
- You can roll back once, but rolling back more than once is highly not recommended, and if need-be, it can be better to flag the post for a diamond moderator's attention, or maybe discuss it on Meta or chat or the comments section before rolling back.
- Starting an edit-war is highly not recommended (and I'll add that it can come with disciplinary measured such as suspensions in some cases). It's better to leave a comment, perhaps including a link to a relevant meta post (such as this one!) or a relevant help center page. If the user doesn't seem to have learned anything, then you can flag for a diamond moderator to take a look.
Q: Limit on editing own answers - different type of edit wars (2011, 211 views)
- There's no official hard-maximum on the number of times you can edit your own answer
- Added by me: Please respect the community though. For example, please don't bump your question over the top of unanswered questions for no reason other than to gain more rep. Like all things, there's exceptions and limitations to the answers given on the page linked above.
I haven't completely read the following, but I selected them from the bigger list of question titles I read when searching about the topic of edit disagreements, because they seemed especially pertinent (hopefully I'll get a chance to read more of the material in these later):
- How should disputes be handled on Stack Overflow? (2009, 478 views)