If you are wondering how to put an image inside a comment box in Diaspora, don't worry, there is a way. It's not immediately obvious how to do it, but yes it's easily possible. Furthermore, you can do the whole thing from inside Diaspora, no need for any other services.
Simply follow the step by step guide below.
1. Before adding your comment, upload an image privately
Decide on an aspect from your Diaspora aspect list that you don't use for anything else. This will be an aspect where you'll only post your pics with no text or commentary; an aspect that doesn't contain any contacts.
Note: If you don't already have an aspect like that, add a new aspect especially for this purpose. This part only has to be done once, not every time you want to add an image. Mine is called "My pics". You can quickly and easily add an aspect on the left hand side of your screen, under "Aspects".
Assuming you now have an aspect for these purposes, make a new post (by clicking on "start a conversation" at the top of the page) but limit it only to your special photo aspect (circled in red). Use the camera icon (circled in green) to upload the pic you want. You don't need to bother including any writing, just the image. It should at this point look like the illustration below:
Then press the "Share" button. Remember, as long as you are only posting it to an aspect where you don't have contacts in it, then no-one will see this image post. Think of it as a private post. The shared post will look something like this.
2. Get the image link from the image you just posted
Right-click on the image you just posted, and select "copy image location".
3. Go to where you want to place a comment containing an image
Find the person's post where you want to put a comment with an image. Let's suppose you want to type some text in it too, start typing. It'll look something like this so far:
You want to include your hamster pic in the comment. So before moving on, click on the image icon circled in red above.
4. Paste image location as the image link in the comment
At this point, when you pressed the image icon, it asks you for a link, like this:
Then in the box, paste the link you got from step 2. Then press the "Comment" button. That's it! You're done. Your comment will contain the image, and it will look something like this:
Conclusion
Yes it's possible to add an image into a comment in the Diaspora social network without using any external services. It's not as easy as adding an image into a regular post on Diaspora, but using the steps outlined above, you can do it.